Each IPv6 node on the network needs a globally unique address to communicate outside its local segment. But where a node get such an address from? There are a few options:

  • Manual assignment - Every node can be configured with an IPv6 address manually by an administrator. It is not a scalable approach and is prone to human error.  
  • DHCPv6 (The Dynamic Host Configuration Protocol version 6) - The most widely adopted protocol for dynamically assigning addresses to hosts. Requires a DHCP server on the network and additional configuration.
  • SLAAC (Stateless Address Autoconfiguration)   -  It was designed to be a simpler and more straight-forward approach to IPv6 auto-addressing. In its current implementation as defined in RFC 4862 , SLAAC does not provide DNS server addresses to hosts and that is why it is not widely adopted at the moment. 

In this lesson, we are going to learn how SLAAC works and what are the pros and cons of using it in comparison to DHCPv6.

What is SLAAC?

SLAAC stands for Stateless Address Autoconfiguration and the name pretty much explains what it does. It is a mechanism that enables each host on the network to auto-configure a unique IPv6 address without any device keeping track of which address is assigned to which node.

Stateless and Stateful in the context of address assignment mean the following:

  • A stateful address assignment involves a server or other device that keeps track of the state of each assignment. It tracks the address pool availability and resolves duplicated address conflicts. It also logs every assignment and keeps track of the expiration times.
  • Stateless address assignment means that  no server keeps track of what addresses have been assigned and what addresses are still available for an assignment. Also in the stateless assignment scenario, nodes are responsible to resolve any duplicated address conflicts following the logic: Generate an IPv6 address, run the Duplicate Address Detection (DAD), if the address happens to be in use, generate another one and run DAD again, etc.

How does SLAAC work?

To fully understand how the IPv6 auto-addressing work, let's follow the steps an IPv6 node takes from the moment it gets connect to the network to the moment it has a unique global unicast address.

Step 1: The node configures itself with a link-local address

When an IPv6 node is connected to an IPv6 enabled network, the first thing it typically does is to auto-configure itself with a link-local address. The purpose of this local address is to enable the node to communicate at Layer 3 with other IPv6 devices in the local segment. The most widely adopted way of auto-configuring a link-local address is by combining the link-local prefix FE80::/64 and the EUI-64 interface identifier, generated from the interface's MAC address. 

Figure 1 shows a step by step example of how a local address is generated from MAC address 7007.1234.5678.

Generating a link-local address from interface's MAC address

Once the above steps are completed, the node has a fully functional EUI-64 format link-local address as shown below:

Step 2: The node performs Duplicate Address Detection (DAD)

After the IPv6 host has its link-local address auto-configured, it has to make sure that the address is actually unique in the local segment. Even though the chances that another node has the same exact address are very slim. It has to perform a process called Duplicate Address Detection (DAD).

DAD is a mechanism that involves a special type of address called solicited-node multicast . Upon configuring an IPv6 address, every node joins a multicast group identified by the address FF02::1:FFxx:xxxx where xx:xxxx are the last 6 hexadecimal values in the IPv6 unicast address. Therefore, for each configured unicast address, no matter if it is link-local or global, the host joins the respective auto-generated solicited-node multicast group.

In our example, the last 6 hexadecimal values of the link-local address are 34:5678 so the node joins the multicast group FF02::1:FF 34:5678 . As PC1 is running a Windows 10 operating system, we can verify that with the following command:

Having this logic in mind, we know that if another host has the same exact link-local address, it will also be listening for messages on the solicited-node multicast group auto-generated from this address - FF02::1:FF34:5678. In order for PC1 to check that, it sends an ICMPv6 message with a destination address set to this group, and the source address set to the IPv6 unspecified address. In the ICMPv6 portion of the packet, PC1 puts the whole address in the Target Address field. Figure 2 illustrates that process. PC1 then sends the packet on the network. Only nodes that are listening to this exact auto-generated multicast group will open the packet, all other nodes will discard it. If any node has an IPv6 address that has the same last 6 hex digits, will look in the ICMPv6 portion and check if the target address matches any of its own addresses. If there is a match, the host will reply back that this IPv6 address is already in use. If nobody replies back, PC1 will conclude that this address is unique and available to be used, and will assign it.

PC1 performs IPv6 DAD for its link-local address

This process is called Duplicate Address Detection (DAD) and is done upon every new address assignment. In our example, PC1 sends the ICMPv6 Neighbor Solicitation message as shown in figure 2, and nobody replies back. PC1 will then know for sure that this link-local address is unique in this local segment.

Step 3: The node sends a Router Solicitation message

Step 1 and 2 in this example depict the process of generating and assigning a unique link-local address. This process is not exactly part of the Stateless Autoconfiguration feature but without a link-local address, PC1 won't be able to communicate at layer 3 with any other IPv6 node. Thus, it is a pre-requisite for the SLAAC to work and that's why we have included it in our example.

After PC1 has a link-local address, it can now start the process of auto-configuring a global unicast address using SLAAC. The first step of this process is to send an ICMPv6 message called Router Solicitation (RS) . The purpose of this message is to ' ask ' all IPv6 routers attached to this segment about the global unicast prefix that is used. The destination address is the all-routers multicast address FF02::2 and for source, PC1 uses its link-local address. Note that only routers are subscribed to multicast group FF02::2, which means that only Router 1 will process this message, and all other nodes on the local segment will discard it.

After Router 1 gets the Router Solicitation message, it responds back with an ICMPv6 message called Router Advertisement (RA). The RA message includes the global IPv6 prefix on the link and the prefix length. In our example, these would be the prefix 2001:1234:A:b:: and the prefix length of /64. For the source of this RA packet, Router 1 uses its own link-local address and destination is the all-nodes multicast address FF02::1. The process is illustrated in figure 3.

Step 4: The node configures its global unicast address

Once PC1 gets back the Router Advertisement from  Router 1, it combines the prefix 2001:1234:A:B::/64 with its EUI-64 interface identifier (7207:12FF:FE34:5678) resulting in the global unicast address 2001:1234:A:B:7207:12FF:FE34:5678/64. Because the Router Advertisement came from Router 1, PC1 sets its IPv6 default gateway to the link-local address of R1.

Now PC1 has a global unicast address and a default gateway. But the SLAAC process is not completed. PC1 must know for sure this auto-generated address is unique in the local segment. Thus, PC1 performs the Duplicate Address Detection (DAD) process. 

Step 5: The node performs Duplicate Address Detection (DAD)

We have already explained the DAD process in detail in step 2. When PC1 auto-generate its global unicast address, it immediately joins the auto-generated solicited-node multicast group FF02::1:FF34:5678. To be sure that nobody else is using this address, PC1 then sends an ICMPv6 message called Neighbor Solicitation to the solicited-node address FF02::1:FF34:5678 and waits to see if a node replies back. If no reply is received back, PC1 knows that this address is unique and can start using it for communication outside its local segment including on the Internet.

The problem with SLAAC

So far so good. We have seen how a node can auto-configure a globally unique IPv6 address and a default gateway.

However, SLAAC does not provide DNS information and without DNS, many services such as surfing the Internet are not possible.  

There is a field in the Router Advertisement header, that is designed to solve this problem.

Router Advertisement Flags

As we said above, by default, SLAAC does not provide DNS. And without DNS, many services that require resolution from URL addresses to IP won't work. There is a field in the RA message that helps nodes understand where to get an IPv6 address and DNS information from. 

Examining the Router Advertisement Flags

If the M-flag is set to 1, it indicates that addresses are available via DHCPv6. The router is basically telling the nodes to ask the DHCP server for addresses and DNS information. If the M flag is set, the O flag can be ignored because DHCPv6 will return all available information.

If the O-flag is set to 1, it indicates that DNS information is available via DHCPv6. The router is basically telling the nodes to auto-configure an address via SLAAC and ask the DHCP server for DNS information.

If neither M nor O flags are set, this indicates that no DHCPv6 server is available on the segment.

The Prf-flag (Default Router Preference) can be set to Low (1), Medium (0), or High(3). When a node receives Router Advertisement messages from multiple routers, the Default Router Preference (DRP) is used to determine which router to prefer as a default gateway.

Examining the Router Advertisement Flags with Wireshark

Configuring SLAAC on Cisco routers

Typically, when IPv6 unicast-routing is enabled on a Cisco router, it starts to send RA messages via all interfaces that have a configured IPv6 global unicast address. 

In our example, when interface GigabitEthernet 0/0 is configured with a global IPv6 unicast address, it immediately starts sending RA messages on the local segment. 

Most parameters can be verified using the show ipv6 interface command

If there is a DHCPv6 server available on the segment, we can set the M-flag or the O-flag in the RA messages using the following options. 

If you'd like to disable the SLAAC feature on this interface, you can use the suppress command under the interface ipv6 options

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IPv6: How to configure static and DHCP IP addressing and deal with DNS

IPv6 offers several ways that aren’t possible in IPv4 to assign IP addresses, and DNS set-up has differences as well.

IPv6 wireless network protocol

As IP technology has matured, the range of devices that the internet protocol supports goes well beyond computers to include cell phones, entertainment systems, and Internet of Things (IoT) devices, which created the need for more IP addresses and the development of IPv6 to provide them.

With more and more device types requiring network connectivity, the demand for addresses in an IPv4-based network is at a premium. It can provide somewhere south of 4,294,967,296 unique addresses. IPv6 , on the other hand, can yield roughly 3.4×10 38 , which should be ample for a very long time.

IPv6 also includes performance enhancements like refined multicasting, stateless address autoconfiguration (SLAAC), simplified headers to streamline router processing, and the option to allow larger packets. Security also gets a potential boost in IPv6 with IPSec, which was initially built for IPv6 and then retrofitted for IPv4.

Dealing with IPv6 includes familiarizing yourself with two important IP concepts: DHCP and DNS. Here are tips on both.

Key IPv6 addressing concepts

IPv6 addressing within a network has a few major differences from IPv4. With IPv4 certain address ranges are reserved for private networks (such as 10.0.0.0/8 or 192.168.0.0/16) and link-local addressing without dynamic host configuration protocol (DHCP) (169.254.0.0/16).

DHCP automatically assigns IP addresses and distributes other information to hosts on a network so they can communicate with other endpoints. At the same time, by assigning active IP addresses only to active devices, DHCP can reuse them to help conserve IPv4 addresses. IPv6 has similar concepts but refines each idea a little further.

Link-local addresses in IPv6 exist on each interface, regardless of whether the interface has an address assigned from DHCP or is configured using another method. Link-local IPv6 addresses have a prefix of fe80::/10 and a 64-bit suffix which can be computed and managed by the host itself without requiring additional networking components. IPv6 hosts can verify the uniqueness of their link-local addresses through a neighbor discovery process, which reaches out to the local network in order to verify that the address is not already in use.

Once a link-local address has been established, the IPv6 host attempts to determine if an IPv6-capable router is available through the use of a router solicitation message. If an IPv6 router is available it will respond with a router advertisement, which includes network configuration information such as a network prefix that is used for automatic address configuration using SLAAC or whether the host should obtain additional configuration information from a DHCPv6 server.

Configuring a Static IPv6 address in Windows

Typical to Windows, there are three ways to configure a static IPv6 address for a network adapter, all of which work in Windows 10 and in both Windows Server 2016 and 2019. The first way uses the classic Control Panel method as follows.

From the Control Panel, navigate to Network and Internet, Network and Sharing Center, and then choose the Change adapter settings link in the left panel. (You can shortcut all the clicking by searching for “View Network Connections” from the Start Menu or the Search bar).

Once you locate the network adapter you wish to configure, you can view the properties and locate the Internet Protocol Version 6 (TCP/IPv6) node and configure the properties for the IPv6 protocol. As with IPv4 you can set the adapter to obtain the IPv6 address automatically or configure your own IPv6 address, subnet, default gateway, and DNS server information. If you need to set multiple IPv6 addresses this can be accomplished by clicking the Advanced button.

The second method of setting a static IP address involves the more modern Settings application. In Settings go to Network & Internet and click the Properties button for the interface you wish to configure. Click the Edit button under IP settings, change the configuration type to Manual, enable IPv6, and populate your settings.

The third way is to use the Windows PowerShell command-line interface. In order to set a static IPv6 address using the New-NetIPAddress cmdlet you will need either the name or the numeric index of the adapter you wish to configure. Both of these values are available using the Get-NetAdapter cmdlet. From an administrative PowerShell prompt enter one of the following commands (on a single line) replacing the details as necessary for your environment:

Managing IPv6 Addressing for a Windows Network

Static IP addresses are generally OK to use when the device is hosting a critical network service that requires retaining a consistent network address, but for general use you’ll want to have a way to automate address configuration.

In an IPv4 network DHCP is the obvious answer for IP configuration and can also provide critical networking details such as the default gateway or DNS-server addresses through DHCP options. IPv6 offers three potential scenarios for managing addressing and network configuration.

SLAAC is a straightforward option assuming your router supports the appropriate router-advertisement messages. DHCP is certainly still in play to handle stateful addressing in the form of DHCPv6. You can also potentially have a hybrid scenario where your router handles addressing, and DHCPv6 simply provides the relevant network-configuration details.

In Windows Server 2016 and 2019, configuring DHCPv6 is extremely straightforward. If your router is configured to handle router advertisements and addressing through SLAAC you can simply manage the IPv6 server options to configure DNS servers or other options. If you prefer to roll with stateful addressing you can add one or more DHCPv6 scopes and configure a prefix, any exclusions, and lease durations. DHCPv6 scopes will maintain a list of leases and their expirations just as an IPv4 scope would, and they also provide an easy path for creating IPv6 reservations from existing leases.

Setting up DNS Name Resolution for IPv6

DNS is incredibly important in an IPv6 network, even moreso than in an IPv4 network because trying to configure connectivity and access resources using only IPv6 addresses is borderline insane. The biggest difference to note in regard to using DNS with IPv6 is that the IPv4 A records, which convert a fully qualified domain name (FQDN) to an IPv4 address, are replaced by AAAA (quad-A) records. All other record types such as CNAME, MX, NS, SOA, and the various DNSSEC-related record types simply reference the FQDN of the AAAA record. Reverse lookup zones, which are used to find a hostname from an IP address, are different in IPv6 simply because they are built on the IP address structure, but the process of creating and using these zones are functionally identical.

The DNS server role in Windows Server supports both IPv4 and IPv6 through a similar set of tools and processes. As with A records, AAAA records can either be created manually for critical systems or the dynamic update process can be leveraged to manage DNS records for the entire enterprise.

AAAA records can be manually created using the DNS console through the same process as A records: Right click the required DNS zone, select the New Host (A or AAAA) option, and populate the Host name and IP address. Dynamic updates are enabled through the DNS console, but most of the work is done by DHCP; the update process is configured within the DHCP console and updates are performed by the DHCP client service on individual hosts. Dynamic updates can also be manually initiated from the command line using the ipconfig command with the /registerdns switch.

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tim_ferrill

Tim Ferrill is an IT professional and writer living in Southern California. He has covered Windows, Windows Phone, and Windows Server for several publications, including CITEworld and InfoWorld.

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IPv6 Dynamic Address Allocation Mechanism Illustrated

IPv6 supports multiple addresses, making address assignments more flexible and convenient. Unlike IPv4, which relied solely on the DHCP protocol for address assignment, IPv6 incorporates a native Stateless Address AutoConfiguration SLAAC) protocol. SLAAC can either work alone to provide IPv6 addresses to hosts, or it can work with DHCPv6 to generate new assignment schemes. Here is a comprehensive analysis of the dynamic address allocation mechanism for IPv6.

Who the hell knew how much address space we needed? — Vint Cerf (American Internet pioneer and one of "the fathers of the Internet")

IPv6 Address Overview

Address formats.

enable automatic ipv6 address assignment

The interface identifier can be generated in several ways:

  • Static manual setting
  • Converted from the interface's MAC address using the modified EUI-64 format
  • Obtained from a DHCPv6 server
  • Automatically established randomly or cryptographically

IETF recommends a canonical textual representation format for ease of writing. It includes leading zeros suppression and compression of consecutive all-zero fields. With the network prefix length at the end, the above address can be shortened to 2001:db8:130f :: 7000: 0 :140b/ 64 .

Address Types

RFC 4291 defines three types of addresses:

  • Unicast: A network address corresponds to a single network node, point-to-point connection.
  • Anycast: The target address corresponds to a group of receiving nodes, but only the "nearest" one receives.
  • Multicast: The target address corresponds to a group of nodes that can receive replicated messages.

Note that there are no broadcast addresses in IPv6, their function being superseded by multicast addresses. Anycast addresses are syntactically indistinguishable from unicast addresses and have very limited applications. A typical application for anycast is to set up a DNS root server to allow hosts to look up domain names in close proximity. For unicast and multicast addresses, they can be identified by different network prefixes:

enable automatic ipv6 address assignment

  • All Nodes Addresses on the local link — ff02::1
  • All Routers Addresses on the local link — ff02::2
  • Solicited-Node Address on local link — ff02::1:ffxx:xxxx

Dynamic Allocation Schemes

Ndp protocol.

IPv6 dynamic address assignment depends on Neighbor Discovery Protocol (NDP). NDP acts at the data link layer and is responsible for discovering other nodes and corresponding IPv6 addresses on the link and determining available routes and maintaining information reachability to other active nodes. It provides the IPv6 network with the equivalent of the Address Resolution Protocol (ARP) and ICMP router discovery and redirection protocols in IPv4 networks. However, NDP adds many improvements and new features. NDP defines five ICMPv6 message types:

  • Router Solicitation (RS)
  • Router Advertisement (RA)
  • Neighbor Solicitation (NS)
  • Neighbor Advertisement (NA)

The first two message types here, RS and RA, are the keys to implementing dynamic IPv6 address assignment. The host sends an RS message to the multicast address ff02::2 of all routers in the local network segment to request routing information. When the router receives the RS from the network node, it sends an immediate RA in response. The message format of the RA is as follows

It defines two special bits, M and O, with the following meaning:

  • M — "Managed address configuration" flag, set to 1 when the address is obtained from DHCPv6.
  • O — "Other configuration" flag, set to 1 to indicate that other configuration information is available via DHCPv6

The RA message ends with the Options section, which originally had three possible options: Source Link-Layer Address, MTU, and Prefix Information. Later, RFC 8106 (which replaced RFC 6106) added the Recursive DNS Server (RDNSS) and DNS Search List (DNSSL) options. The Prefix Information option directly provide hosts with on-link prefixes and prefixes for Address Autoconfiguration, and it has the following format

Here the Prefix Length and the Prefix jointly determine the network prefix of the IPv6 address. In addition, the Prefix Information option also defines two special bits, L and A:

  • L — on-link flag. When set, indicates that this prefix can be used for on-link determination.
  • A — autonomous address-configuration flag. When set, indicates that this prefix can be used for SLAAC.

Similar to the IPv4 subnet mask feature, the purpose of the "on-link" determination is to allow the host to determine which networks an interface can access. By default, the host only considers the network where the link-local address is located as "on-link". If the "on-link" status of a destination address cannot be determined, the host forwards the IPv6 datagram to the default gateway (or default router) by default. When the host receives an RA message, if the "on-link" flag for a prefix information option is set to 1 and the Valid Lifetime is also a non-zero value, the host creates a new prefix network entry for it in the prefix list. All unexpired prefix network entries are "on-link".

Message Sequence

After understanding the NDP protocol and the information conveyed by the RA messages, let's see how they guide the network nodes to achieve dynamic address assignment.

Routers in the network periodically send RA messages to the multicast addresses (ff02::1) of all nodes in the local subnet. However, to avoid latency, the host sends one or more RS messages to all routers in the local subnet as soon as it has finished booting. The protocol requires the routers to respond to the RA messages within 0.5 seconds. Then, based on the values of the M/O/A bits in the received RA messages, the host decides how to dynamically configure the unique local and global unicast addresses of the interface and how to obtain other configuration information. With certain combinations of bit fetch values, the host needs to run DHCPv6 client software to connect to the server to obtain address assignment and/or other configuration information. The entire process is shown in the following message sequence diagram.

Note: Unlike the IPv4 DHCP protocol, DHCPv6 clients use UDP port 546 and servers use UDP port 547.

Next explain in detail three dynamic allocation schemes determined by the combination of the M/O/A-bit values:

SLAAC + Stateless DHCPv6

Stateful dhcpv6.

SLAAC is the simplest automatic IPv6 address assignment scheme and does not require any server. It works by sending an RS message request after the host starts up and the router sends back RA messages to all nodes in the local network segment. If the RA message contains the following configuration

  • M-bit and O-bit all clear in the message header
  • L-bit and A-bit all set in Prefix Information option

Then the host receives this RA message and performs the following operations to implement SLAAC:

  • Combine the network prefix with the local interface identifier to generate a unique local address or global unicast address.
  • Install the default gateway (or default route) to point to the router address (source address of the RA message).
  • Set this interface as the "on-link" corresponding to the network prefix, which is also the next-hop interface of the default gateway above.
  • If the RDNSS and/or DNSSL options are included, install the name servers and domain name suffixes.

This way, the host gets one or more IPv6 unique local addresses or global unicast addresses, plus the default gateway and domain name service information to complete various Internet connections.

The following is an example of the SLAAC configuration on a Cisco Catalyst 9300 Multilayer Access Switch:

The Layer 3 interface of the Cisco Multilayer Switch provides routing functionality. As you can see, when IPv6 is activated on the Layer 3 interface in VLAN 10, its default address auto-assignment scheme is SLAAC. the control bits of RA messages from this interface are all set according to the SLAAC scheme, and the network prefixes for each IPv6 address it configures are automatically added to the RA prefix information options list. Of course, the network administrator can also exclude certain network prefixes with a separate interface configuration command. The last two lines of the example configuration command specify RDNSS and DNSSL, which are also added to the RA message options.

If a host connects to a port in VLAN 10, it immediately gets a global unicast address with the network prefix of 2001:ABCD:1000::/64, and its default gateway address is set to 2001:ABCD:1000::1. Open a browser and enter a URL, and it will send a message to the specified domain name server 2001:4860:4860::8888 (Google's public name server address) to obtain the IPv6 address of the destination URL to establish a connection.

SLAAC automatic address assignment is fast and easy, providing a plug-and-play IPv6 deployment solution for small and medium-sized network deployments. However, if a network node needs access to additional configuration information, such as NTP/SNTP server, TFTP server, and SIP server addresses, or if its functionality relies on certain Vendor-specific Information Options, it must choose SLAAC + stateless DHCPv6 scheme.

This scenario still uses SLAAC automatic address assignment, but the router instructs the host to connect to a DHCPv6 server for additional configuration information. At this point, the RA message sent back by the router has

  • M-bit clear and O-bit set in the message header

After receiving this RA message, the host performs the following actions:

  • Install a default gateway (or default route) pointing to the router address (source address of the RA message).
  • Start the DHCPv6 client and connect to the DHCPv6 server to request additional configuration information .
  • Save the additional configuration information replied by the DHCPv6 server .

As you can see, SLAAC + stateless DHCPv6 is not different from SLAAC in terms of address assignment. DHCPv6 only provides additional configuration information and does not assign IPv6 addresses. So the DHCPv6 server does not track the address assignment status of network nodes, which is what "stateless" means.

The corresponding configuration commands on the Catalyst 9300 switch are as follows.

The difference with the SLAAC example is that the VLAN 10 interface configuration command ipv6 nd other-config-flag explicitly specifies to set the O-bit of the RA message. Its next command, ipv6 dhcp server vlan-10-clients , activates the DHCPv6 server response feature of the interface, corresponding to the server's pool name of vlan-10-clients . The DHCPv6 server is configured above the interface configuration, starting at ipv6 dhcp pool vlan-10-clients , and contains the DNS server address, DNS domain name, and SNTP server address.

If you are using a separate DHCPv6 server located on a network segment, you can remove the ipv6 dhcp server command and enable the ipv6 dhcp relay destination command on the next line of the example to specify the address to forward DHCPv6 requests to the external server.

Many large enterprises use DHCP to manage the IPv4 addresses of their devices, so deploying DHCPv6 to centrally assign and manage IPv6 addresses is a natural preference. This is where Stateful DHCPv6 comes into play. This scenario also requires RA messages sent by the router but does not rely solely on network prefixes for automatic address assignment. The control bits of the RA messages are configured to

  • M-bit set in the message header, O-bit does not matter
  • L-bit and A-bit can be set or clear as desired in Prefix Information option

Upon receiving this RA message, the host performs the following actions:

  • Generate a unique local address or a global unicast address if there is a Prefix Information option with the A-bit set.
  • If there is a Prefix Information option with the L-bit set, set this interface to "on-link" with the corresponding network prefix.
  • If the RDNSS and/or DNSSL options are included, install the name servers and domain suffixes.
  • Start the DHCPv6 client and connect to the server to request addresses and other configuration information .
  • Set the address assigned by the DHCPv6 server to this interface .
  • Save additional configuration information from the DHCPv6 server response .

An example of the Stateful DHCPv6 configuration command on a Catalyst 9300 switch is as follows.

Compared to SLAAC + Stateless DHCPv6 , the interface configuration here removes the ipv6 nd other-config-flag and replaces it with the ipv6 nd managed-config-flag command. This corresponds to setting the M-bit of the RA message header. The DHCPv6 server configuration adds two address prefix commands to set the network prefix. Also, the ipv6 nd prefix 2001:ABCD:1:1::/64 no-advertise configured for the interface specifies that the router does not include the 2001:ABCD:1:1::/64 prefix information option into the RA. So, this example host interface will not generate SLAAC addresses, but only two addresses from DHPCv6: a unique local address with the network prefix FD09:9:5:90::/64, and a global unicast address with the network prefix 2001:9:5:90::/64. The interface identifier for each of these two addresses is also specified by DHPCv6.

How to distinguish the source of dynamically assigned addresses for host interfaces? The method is simple. One thing to remember is that DHPCv6 does not send the network prefix length to the requestor, so the network prefix length of the addresses received from DHPCv6 is 128, while the network prefix length of the addresses generated by SLAAC will not be 128. See the following example of the wired0 interface on a Linux host:

We can immediately determine that the interface is using Stateful DHCPv6 address assignment, but also generates the SLAAC address with the same network prefix 2001:20::/64 received.

  • 2001:20::53c7:1364:a4d8:fd91/128 — DHCPv6 address, random interface identifer
  • 2001:20::a2ec:f9ff:fe6c:d930/64 — SLAAC addeess, interface identifer is MAC in EUI-64 format
  • fe80::a2ec:f9ff:fe6c:d930/64 — Link-local address, interface identifer is MAC in EUI-64 format

Note: DHPCv6 server also does not provide any IPv6 default gateway information. The host needs to be informed of the dynamic default gateway from the RA message.

Summary and Comparison

The following table shows the control bit combinations of RA messages concerning different address allocation and other configuration acquisition methods.

Summarize three dynamic allocation schemes:

Note: Since IPv6 network interfaces can have multiple addresses (a link-local address, plus one or more unique local addresses and/or global unicast addresses), it becomes important how the source address is selected when establishing an external connection. RFC 6724 gives detailed IPv6 source address selection rules. In the development of embedded systems, the control plane and the data plane connected to the same remote device are often implemented by different functional components. For example, the control plane directly calls a Linux userspace socket to establish the connection, and the IPv6 source address used for the connection is selected by the TCP/IP stack, while the data plane directly implements data encapsulation processing and transmission in kernel space. In this case, the IPv6 source address selected by the control plane has to be synchronized to the data plane in time, otherwise, the user data might not be delivered to the same destination.

Troubleshooting Guide

The common IPv6 dynamic address assignment debugging and troubleshooting commands on Cisco routers and switches are listed in the following table.

The following console NDP protocol debug log shows that the router received an RS message from host FE80::5850:6D61:1FB:EF3A and responded with an RA message to the multicast address FF02::1 of all nodes in this network:

And the next log shows an example of Stateless DHCPv6 observed after entering the debug ipv6 dhcp debug command. Host FE80::5850:6D61:1FB:EF3A sends an INFORMATION-REQUEST message to the DHCPv6 server, which selects the source address FE80::C801:B9FF:FEF0:8 and sends a response message.

The following debug log of Stateful DHCPv6 shows the complete process of two message exchanges (SOLICIT/ADVERTISE, REQUEST/REPLY) on lines 1, 15, 16, and 26.

For complex cases where it is difficult to identify whether the problem is with the host, router, or DHCPv6 server, we recommend using the free open-source network packet analysis software Wireshark to capture packets of the entire process for analysis. While analyzing packets with Wireshark, you can apply the keyword filtering function.

We can either run Wireshark directly on the host side, or we can use the Switched Port Analyzer (SPAN) provided with the switch. Running on the network side, SPAN can collectively redirect packets from a given port to the monitor port running Wireshark for capturing. Cisco Catalyst 9300 Series switches also directly integrate with Wireshark software to intercept and analyze filtered packets online, making it very easy to use.

Sample packet capture files for three allocation scheme are available here for download and study: slaac.pcap , stateless-dhcpv6.pcap , stateful-dhcpv6.pcap

IPv6 Product Certification Test

Accurate and effective testing of IPv6 products is key to ensuring high interoperability, security, and reliability of IPv6 infrastructure deployments. The IPv6 Ready logo is an IPv6 testing and certification program created by the IPv6 Forum . Its goals are to define IPv6 conformance and interoperability test specifications, provide a self-testing toolset, establish Global IPv6 Test Centers and provide product validation services, and finally, issue IPv6 Ready logo.

In May 2020, IPv6 Ready Logo Program published new version 5.0 test specifications :

  • IPv6 Core Protocols Test Specification (Conformance)
  • IPv6 Core Protocols Interoperability Test Specification (Interoperability)

Along with these two new test specifications, the project team also affirmed two permanent changes:

  • Testing must be done in an IPv6-only environment, without any IPv4 being used for the device to function.
  • The device under test must have IPv6 on and enabled on all IP interfaces by default.

Not surprisingly, the new version 5.0 core protocols test specification has a section dedicated to defining SLAAC test cases to validate this core IPv6 protocol.

IPv6 Core Protocol RFC List

In the list below, the RFCs shown in bold are directly covered by the IPv6 Ready Version 5.0 Core Protocol Test Specification:

  • RFC 4191 Default Router Preferences and More-Specific Routes
  • RFC 4193 Unique Local IPv6 Unicast Addresses
  • RFC 4291 IP Version 6 Addressing Architecture
  • RFC 4443 Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification
  • RFC 4861 Neighbor Discovery for IP version 6 (IPv6)
  • RFC 4862 IPv6 Stateless Address Autoconfiguration
  • RFC 4941 Privacy Extensions for Stateless Address Autoconfiguration in IPv6
  • RFC 5095 Deprecation of Type 0 Routing Headers in IPv6
  • RFC 6724 Default Address Selection for Internet Protocol Version 6 (IPv6)
  • RFC 6980 Security Implications of IPv6 Fragmentation with IPv6 Neighbor Discovery
  • RFC 7217 A Method for Generating Semantically Opaque Interface Identifiers with IPv6 Stateless Address Autoconfiguration (SLAAC)
  • RFC 8064 Recommendation on Stable IPv6 Interface Identifiers
  • RFC 8106 IPv6 Router Advertisement Options for DNS Configuration
  • RFC 8200 Internet Protocol, Version 6 (IPv6) Specification
  • RFC 8201 Path MTU Discovery for IP version 6
  • RFC 8415 Dynamic Host Configuration Protocol for IPv6 (DHCPv6)
  • Gitalk Comments
  • Utterances Comments
  • Disqus Comments

IPv6 Address Assignment Example

Lesson Contents

In this lesson we’ll take a look how you can create IPv6 prefixes and subnets so that you can configure your entire network with IPv6. We’ll start at the top where IANA (Internet Assigned Numbers Authority) is responsible for the global coordination of the IPv4 and IPv6 address space and move our way all the way to the bottom where we assign subnets and IPv6 addresses to our routers, switches and VLANs.

IPv6 Global Unicast Prefix Assignments

IANA “owns” the entire IPv6 address space and they assign certain prefixes to the RIRs (Regional Internet Registry). There are 5 RIRs at the moment:

rir map

  • AFRINIC : Africa
  • APNIC : Asia/Pacific
  • ARIN : North America
  • LACNIC : Latin America and some Caribbean Islands
  • RIPE NCC : Europe, Middle east and Central Asia

If you are interested, click here for an overview of all IPv6 prefix assignments by IANA.

When a large ISP (or large company) in North America wants IPv6 addresses then they will contact ARIN who will assign them an IPv6 prefix if they meet all requirements. The ISP can then assign prefixes to their customers.

Let’s take a look at some actual prefixes:

IPv6 prefix assignment

  • IANA is using the 2000::/3 prefix for global unicast address space.
  • According to this list, RIPE NCC received prefix 2001:4000::/23 from IANA.
  • A large ISP called Ziggo in The Netherlands receives prefix 2001:41f0::/32 from RIPE NCC.
  • The ISP assigns prefix 2001:41f0:4060::/48 to one of their customers.

Now it’s up to the customer what they want to do with their IPv6 prefix…

IPv6 Global Unicast Subnet Assignments

Our customer received prefix 2001:41f0:4060::/48 and they want to use it to configure IPv6 on their entire network. Where do we start? Take a look at the image below:

IPv6 Global Routing Prefix Subnet Interface ID

The 48-bit prefix that we received is typically called the global routing prefix or site prefix . The interface ID is normally 64 bit which means we have 16 bits left to create subnets .

If I want I can steal some more bits from the Interface ID to create even more subnets but there’s no need for this. Using 16 bits we can create 65.536 subnets …more than enough for most of us. Let’s see what we can do for our customer:

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Forum Replies

Rene, just to be clear, they aren’t the same right? 2001:41f0:4060:10::/64 and 2001:41f0:4060:A::/64 ?

That’s right.

shouldn’t this be /64 ?

Yes that’s right, just fixed it. Thanks!

Why are these not the same

2001:41f0:4060:10::/64 and 2001:41f0:4060:A::/64 ?

45 more replies! Ask a question or join the discussion by visiting our Community Forum

Configuring IPv6 address autoconfiguration

  • In System i Navigator , expand your system > Network > TCP/IP Configuration > Lines .
  • Right-click one of the lines in the right pane, and select IPv6 Stateless Address Autoconfiguration > Configure .
  • Follow the steps in the New IPv6 Interface wizard to complete the autoconfiguration.
  • To start the IPv6 interface created by the autoconfiguration, right-click the line you just configured and select IPv6 Stateless Address Autoconfiguration > Start . Note: To ensure that the IPv6 is started automatically when you start TCP/IP, select Start when TCP/IP is started in the Configure Line for IPv6 display.

If the status changes to Active, you have configured and started the IPv6 address autoconfiguration successfully.

  • On the command line, type ADDTCPIFC (Add TCP/IP Interface command) and press F4 (Prompt) to access the Add TCP/IP Interface menu.
  • At the Internet address prompt, type *IP6SAC .
  • At the Line description prompt, specify a line name (use any name), and press Enter to see a list of optional parameters.
  • Specify any of the optional parameters, and then press Enter.

To start the IPv6 stateless address autoconfiguration, follow these steps:

  • On the command line, type STRTCPIFC (Start TCP/IP Interface command) and press F4 (Prompt) to access the Start TCP/IP Interface menu.
  • At the Internet address prompt, type *IP6SAC , and press Enter.
  • At the Line description prompt, specify the line name that you defined in the preceding configuration steps, and then press Enter.

You have successfully configured and started the IPv6 address autoconfiguration.

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ipv6-configuration

Table of Contents

IPv6 Configuration

IPv6 is the new version of the most important Network Layer Protocol IP. With this new IP version, IPv6, beside different features, some configuration differencies are also coming. In this lesson, we will focus on these IPv6 Configuration Steps, IPv6 Configuration on Cisco devices . We will use the below Packet Tracer topology for our IPv6 Config .

You can download Packet Tracer IPv6 Lab , in Packet Tracer Labs page.

In this configuration lesson, we will follow the below IPv6 Configuration steps :

Enable IPv6 Globally

Enable ipv6 on interface, configure eui-64 format global unicast address, configure manual global unicast address, manual link local address configuration, auto ipv6 address configuration, enable dhcpv6 client, ipv6 verification commands.

  So, let’s go to the IPv6 Configuration steps and configure IPv6 for Cisco routers .

After going to the configuration mode with “ configure terminal ” command, to enable IPv6 on a Cisco router, “ ipv6 unicast-routing ” command is used. With this Cisco command, IPv6 is enabled globally on the router. This can be used before both interface configurations and IPv6 Routing Protocol configurations.

Router 1# configure terminal Router 1(config)# ipv6 unicast-routing Router 2# configure terminal Router 2(config)# ipv6 unicast-routing

After enabling IPv6 globally, we should enable IPv6 under the Interfaces. To enable IPv6 under an interface, we will use “ ipv6 enable ” command. Let’s enable IPv6 on two interfaces of each router.

Router 1 (config)# interface FastEthernet0/0 Router 1 (config-if)# ipv6 enable Router 1 (config-if)# no shutdown Router 1 (config)# interface FastEthernet0/1 Router 1 (config-if)# ipv6 enable Router 1 (config-if)# no shutdown
Router 2 (config)# interface FastEthernet0/0 Router 2 (config-if)# ipv6 enable Router 2 (config-if)# no shutdown Router 2 (config)# interface FastEthernet0/1 Router 2 (config-if)# ipv6 enable Router 2 (config-if)# no shutdown

EUI-64 format is the IPv6 format used to create IPv6 Global Unicast Addresses . It is a specific format that we have also talked about before. With this format, basically, interface id of the whole IPv6 adderess is ceated with the help of the MAC address. After that, this created interface id is appended to the network id.

To configure an interface with EUI-64 format (Extended Unique Identifier), firstly we will go under the interface, then we will use “ ip address ipv6-address/prefix-length eui-64 ” command. Here, our IPv6 address and prefix-length are 2001:AAAA:BBBB:CCCC::/64. The real EUI-64 Global Unicast Address will be created with this address and MAC address after IPv6 configuration.

Router 1 (config)# interface FastEthernet0/0 Router 1(config-if)# ipv6 address 2001:AAAA:BBBB:CCCC::/64 eui-64 Router 1(config-if)# end

Let’s check the IPv6 address that is created with EUI-64 format with “ show ipv6 interface brief ” command.

Router 1# show ipv6 interface brief FastEthernet0/0            [up/up] FE80::2E0:B0FF:FE0E:7701 2001:AAAA:BBBB:CCCC:2E0:B0FF:FE0E:7701 FastEthernet0/1            [up/up] FE80::2E0:B0FF:FE0E:7702 Vlan1                      [administratively down/down] unassigned

If we do not use EUI-64 format address, we have to write the whole IPv6 Address to the configuration line. Let’s configure Gigabit Ethernet 0/0 interface of Router 2 manually .

Router 2 (config)# interface FastEthernet0/0 Router 2 (config-if)# ipv6 address 2001:AAAA:BBBB:CCCC:1234:1234:1234:1234/64 Router 2(config-if)# end

Here, both of these directly connected interfaces are in the same subnet, the Network ID is same (2001:AAAA:BBBB:CCCC::/64).

Let’s check the IPv6 address that we have manually assigned with “ show ipv6 interface brief ” command.

Router 2# show ipv6 interface brief FastEthernet0/0            [up/up] FE80::206:2AFF:FE15:BD01     2001:AAAA:BBBB:CCCC:1234:1234:1234:1234 FastEthernet0/1            [administratively up/up] FE80::206:2AFF:FE15:BD02 Vlan1                      [administratively down/down] unassigned

To check the connectivity between two node, we use ping. As IPv4, with IPv6, we also use ping, but this time it is called IPv6 Ping . The format of IPv6 Ping is a little difference than IPv4 Ping. These  differences are the format of the used IP address and the used keywords. With IPv6 Ping , “ ping ipv6 ” keywords are used before the destination IPv6 address.

Here, we will ping from Router 1 GigabitEthernet0/0 interface to Router 2 GigabitEthernet0/0 interface.

Router 1# ping ipv6 2001:AAAA:BBBB:CCCC:1234:1234:1234:1234   Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 2001:AAAA:BBBB:CCCC:1234:1234:1234:1234, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 0/0/1 ms

To check the configured IPv6 Address, we can use “ show ipv6 interface interface-name ” command.

Router 1# show ipv6 interface FastEthernet0/0 FastEthernet0/0 is up, line protocol is up IPv6 is enabled, link-local address is FE80::2E0:B0FF:FE0E:7701 No Virtual link-local address(es): Global unicast address(es): 2001:AAAA:BBBB:CCCC:2E0:B0FF:FE0E:7701 , subnet is 2001:AAAA:BBBB:CCCC::/64 [EUI] Joined group address(es): FF02::1 FF02::2 FF02::1:FF0E:7701 MTU is 1500 bytes ICMP error messages limited to one every 100 milliseconds ICMP redirects are enabled ICMP unreachables are sent ND DAD is enabled, number of DAD attempts: 1 ND reachable time is 30000 milliseconds ND advertised reachable time is 0 (unspecified) ND advertised retransmit interval is 0 (unspecified) ND router advertisements are sent every 200 seconds ND router advertisements live for 1800 seconds ND advertised default router preference is Medium Hosts use stateless autoconfig for addresses.
Router 2# show ipv6 interface FastEthernet0/0 FastEthernet0/0 is up, line protocol is up IPv6 is enabled, link-local address is FE80::206:2AFF:FE15:BD01 No Virtual link-local address(es): Global unicast address(es):     2001:AAAA:BBBB:CCCC:1234:1234:1234:1234 , subnet is 2001:AAAA:BBBB:CCCC::/64 Joined group address(es): FF02::1 FF02::2 FF02::1:FF15:BD01 FF02::1:FF34:1234 MTU is 1500 bytes ICMP error messages limited to one every 100 milliseconds ICMP redirects are enabled ICMP unreachables are sent ND DAD is enabled, number of DAD attempts: 1 ND reachable time is 30000 milliseconds ND advertised reachable time is 0 (unspecified) ND advertised retransmit interval is 0 (unspecified) ND router advertisements are sent every 200 seconds ND router advertisements live for 1800 seconds ND advertised default router preference is Medium Hosts use stateless autoconfig for addresses.

Here, with ipv6 ping, there are some options that we can use. These are given below:

ping ipv6 [hostname | ip_address] [repeat repeat-count | size datagram-size | source [ interface-name | source-address ]

  • repeat : Ping packet count. The default ping repeat value is 5.
  • size : Datagram size. The default value ping size is 56 bytes.
  • source : Source Address of the ping. Default value is None.

So if we would like to send 10 IPv6 ping packet with 200 byte datagrams from 2001:AAAA:BBBB:CCCC:1234:1234:1234:1234 to 2001:AAAA:BBBB:CCCC:1111:2222:3333:4444, we will use the below command:

Router 2 # ping ipv6 2001:AAAA:BBBB:CCCC:1111:2222:3333:4444 repeat 10 size 200 source 2001:AAAA:BBBB:CCCC:1234:1234:1234:1234

To configure a Link Locak address manually, we use “ ipv6 address link-local ipv6-address ” command. Here, we should write an IPv6 address in the range of Link Local addresses. If you would like to learn more about a Link Local Address, you can check Link Local Address lesson.

Let’s configure GigabitEthernet0/1 interface of Router 1 with Link Local Address FE80::AAAA:BBBB:CCCC:DDDD. Here, there is no need to write a prefix length but we will add link-local keyword at the end of the command.

Router 1 (config)# interface FastEthernet0/1 Router 1 (config-if)# ipv6 address FE80::AAAA:BBBB:CCCC:DDDD link-local Router 1 (config-if)# end

Let’s check the manually configure ipv6 Link-Local address with “ show ipv6 interface brief ” command.

Router 1# show ipv6 interface brief FastEthernet0/0            [up/up] FE80::2E0:B0FF:FE0E:7701 2001:AAAA:BBBB:CCCC:2E0:B0FF:FE0E:7701 FastEthernet0/1            [administratively down/down]     FE80::AAAA:BBBB:CCCC:DDDD Vlan1                      [administratively down/down] unassigned

IPv6 Addresses can be configured automatically. This is one of the most important characteristics coming with IPv6. For IPv6 Auto configuration , we will use “ ipv6 address autoconfig ” command. Let’s use it on Router 2 on GigabitEthernet0/1.

Router 2 (config)# interface FastEthernet0/1 Router 2 (config-if)# ipv6 address autoconfig Router 2 (config-if)# end

This type of IPv6 address configuration is Sateless Auto Configuration .

Let’s check the Autoconfigured Link-Local ipv6 address with “ show ipv6 interface brief ” command.

Router 2# show ipv6 interface brief FastEthernet0/0            [up/up] FE80::206:2AFF:FE15:BD01 2001:AAAA:BBBB:CCCC:1234:1234:1234:1234 FastEthernet0/1            [up/down]     FE80::206:2AFF:FE15:BD02 Vlan1                      [administratively down/down] unassigned

Let’s ping from Router 2 to Router 1 to test this second interfaces’ ipv6 connection.

Router 2# ping ipv6 FE80::AAAA:BBBB:CCCC:DDDD Output Interface: FastEthernet0/1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to FE80::AAAA:BBBB:CCCC:DDDD, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 0/0/1 ms

To enable DHCPv6 Client function on an interface, we use “ ipv6 address dhcp ” command under this interface. With this command, interface gets its IPv6 address form the DHCPv6 server . Let’s enable DHCPv6 on GigabitEthernet0/2 of Router 2.

Router 1 (config)# interface FastEthernet0/1 Router 1 (config-if)# ipv6 address dhcp Router 1 (config)# end

To verify DHCPv6 enabled interfaces, we can use “ show ipv6 dhcp interface ” command.

Router 1 # show ipv6 dhcp interface

To verify IPv6 Configuration, we can use different show commands. These IPv6 show commands are given below

  • To check IPv6 interface configuration and status we use “ show ipv6 interface interface-id ”.
Router 1# show ipv6 interface FastEthernet0/0 FastEthernet0/0 is up, line protocol is up IPv6 is enabled, link-local address is FE80::2E0:B0FF:FE0E:7701 No Virtual link-local address(es): Global unicast address(es): 2001:AAAA:BBBB:CCCC:2E0:B0FF:FE0E:7701, subnet is 2001:AAAA:BBBB:CCCC::/64 [EUI] Joined group address(es): FF02::1 FF02::2 FF02::1:FF0E:7701 MTU is 1500 bytes ICMP error messages limited to one every 100 milliseconds ICMP redirects are enabled ICMP unreachables are sent ND DAD is enabled, number of DAD attempts: 1 ND reachable time is 30000 milliseconds ND advertised reachable time is 0 (unspecified) ND advertised retransmit interval is 0 (unspecified) ND router advertisements are sent every 200 seconds ND router advertisements live for 1800 seconds ND advertised default router preference is Medium Hosts use stateless autoconfig for addresses.
  • To check IPv6 neighbor cache entries we use “ show ipv6 neighbors ”.
Router 1# show ipv6 neighbors IPv6 Address                              Age Link-layer Addr State Interface 2001:AAAA:BBBB:CCCC:1234:1234:1234:1234    23 0006.2A15.BD01  REACH Fa0/0 FE80::206:2AFF:FE15:BD02                    7 0006.2A15.BD02  REACH Fa0/1
  • To check IPv6 Routing Table we use “ show ipv6 route ”.
Router 1# show ipv6 route   IPv6 Routing Table – 3 entries Codes: C – Connected, L – Local, S – Static, R – RIP, B – BGP U – Per-user Static route, M – MIPv6 I1 – ISIS L1, I2 – ISIS L2, IA – ISIS interarea, IS – ISIS summary O – OSPF intra, OI – OSPF inter, OE1 – OSPF ext 1, OE2 – OSPF ext 2 ON1 – OSPF NSSA ext 1, ON2 – OSPF NSSA ext 2 D – EIGRP, EX – EIGRP external C   2001:AAAA:BBBB:CCCC::/64 [0/0] via ::, FastEthernet0/0 L   2001:AAAA:BBBB:CCCC:2E0:B0FF:FE0E:7701/128 [0/0] via ::, FastEthernet0/0 L   FF00::/8 [0/0] via ::, Null0
  • To check IPv6 DHCP we use “ show ipv6 dhcp ”.
Router 1# show ipv6 dhcp This device’s DHCPv6 unique identifier (DUID): 0003000100E0B00E7701
  • To check IPv6 Protocols we use “ show ipv6 protocols ”.
Router 1# show ipv6 protocols IPv6 Routing Protocol is “connected” IPv6 Routing Protocol is “static

Questions For IPv6 Configuration

Question 1: with which command do we enable ipv6 globally for ipv6 configuration.

a) ipv6 enable

b) ipv6 unicast-routing

c) ipv6 no shutdown

d) ipv6 run

Question 2: Which command enables IPv6 under an interface?

Question 3: which command enables auto ipv6 addressing under an interface .

a) ipv6 auto

d) ipv6 address autoconfig

e) ipv6 run

Question 4: Which command enables DHCPv6 under an interface?

a) ipv6 auto dhcp

b) ipv6 address dhcp

c) ipv6 address autoconfig

d) ipv6 dhcp run

e) ipv6 dhcp on

Question 5: How to send 20 ping packet to 001:AAAA:BBBB:CCCC:1111:2222:3333:4444 address?

a) ping ipv6 2001:AAAA:BBBB:CCCC:1111:2222:3333:4444 source 20

b) ping ipv6 2001:AAAA:BBBB:CCCC:1111:2222:3333:4444 size 20

c) ping ipv6 2001:AAAA:BBBB:CCCC:1111:2222:3333:4444 repeat 20

Answers: 1) b     2) a    3) d    4) b    5) c   

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enable automatic ipv6 address assignment

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Dynamically Assigning IPv6 Addresses

IPv6 addresses are used to deal with IPv4 address exhaustion. If an ECS uses an IPv4 address, the ECS can run in dual-stack mode after IPv6 is enabled for it. Then, the ECS will have two IP addresses to access the intranet and Internet: an IPv4 address and an IPv6 address.

In some cases, an ECS cannot dynamically acquire an IPv6 address even if it meets all the requirements in Constraints . You need to configure the ECS to dynamically acquire IPv6 addresses. For public images:

  • By default, dynamic IPv6 address assignment is enabled for Windows public images. You do not need to configure it. The operations in Windows Server 2012 and Windows Server 2008 are for your reference only.
  • Before enabling dynamic IPv6 address assignment for a Linux public image, check whether IPv6 has been enabled and then whether dynamic IPv6 address assignment has been enabled. Currently, IPv6 is enabled for all Linux public images.

Constraints

For details about how to enable IPv6 on a subnet, see Enabling IPv6 on the Subnet Where the ECS Works .

enable automatic ipv6 address assignment

If the value of IPv6 is Yes for an ECS flavor, the flavor supports IPv6.

enable automatic ipv6 address assignment

AZ and Flavor determine whether IPv6 is supported.

After you select an AZ, if IPv6 is not displayed or the value of IPv6 is No , IPv6 is not supported by any or certain flavors in the AZ.

enable automatic ipv6 address assignment

  • After the ECS is started, its hot-swappable NICs cannot automatically acquire IPv6 addresses.
  • Only ECSs can work in dual-stack mode and BMSs cannot.
  • Only one IPv6 address can be bound to a NIC.
  • Windows: Windows Server 2012/2008 is used as an example to describe how to enable dynamic assignment of IPv6 addresses in Windows.

If a private image created from a CentOS 6.x or Debian ECS with automatic IPv6 address assignment enabled is used to create an ECS in an environment that does not support IPv6, the ECS may start slow because of IPv6 address assignment timeout. You can set the timeout duration for assigning IPv6 addresses by referring to Setting the Timeout Duration for IPv6 Address Assignment .

Enabling IPv6 on the Subnet Where the ECS Works

  • Log in to the management console.

enable automatic ipv6 address assignment

  • Click the target ECS to go to the detail page.
  • In the ECS Information area, click the VPC name.

The Subnets page is displayed.

The subnet details page is displayed.

  • In the Subnet Information area, click Enable for IPv6 CIDR Block .
  • Click Yes .

Windows Server 2012

Run the following command in the CMD window to check it:

enable automatic ipv6 address assignment

By default, dynamic IPv6 address assignment is enabled for Windows public images, as shown in Figure 3 . No additional configuration is required.

  • Choose Start > Control Panel .
  • Click Network and Sharing Center .

enable automatic ipv6 address assignment

  • In the Ethernet Status dialog box, click Properties in the lower left corner.

enable automatic ipv6 address assignment

  • Perform 1 to check whether dynamic IPv6 address assignment is enabled.
  • IPv6 address : IPv6 address allocated during ECS creation. Obtain the value from the ECS list on the console.
  • Subnet prefix length : 64
  • Preferred DNS server : 240c::6666 (recommended)

enable automatic ipv6 address assignment

For Windows Server 2012, run the following command in PowerShell or CMD:

Set-NetIPv6Protocol -RandomizeIdentifiers disabled

Windows Server 2008

enable automatic ipv6 address assignment

By default, dynamic IPv6 address assignment is enabled for Windows public images, as shown in Figure 9 . No additional configuration is required.

  • Click Change adapter settings .
  • Right-click the local network connection and choose Properties .

enable automatic ipv6 address assignment

  • Choose Start > Control Panel > Network Connection > Local Connection .

enable automatic ipv6 address assignment

For Windows Server 2008, run the following command in PowerShell or CMD:

netsh interface ipv6 set global randomizeidentifiers=disable

Disable the local connection and then enable it again.

To disable the local connection, choose Start > Control Panel > Network and Internet > Network and Sharing Center > Change Adapter Options . Right-click the local connection and choose Disable from the shortcut menu.

To enable the local connection, choose Start > Control Panel > Network and Internet > Network and Sharing Center > Change Adapter Options . Right-click the local connection and choose Enable from the shortcut menu.

Linux (Automatically Enabling Dynamic Assignment of IPv6 Addresses)

The ipv6-setup- xxx tool can be used to enable Linux OSs to automatically acquire IPv6 addresses. xxx indicates a tool, which can be rhel or debian.

You can also enable dynamic IPv6 address assignment by following the instructions in Linux (Manually Enabling Dynamic Assignment of IPv6 Addresses) .

enable automatic ipv6 address assignment

  • When you run ipv6-setup- xxx , the network service will be automatically restarted. As a result, the network is temporarily disconnected.

If a private image created from a CentOS 6.x or Debian ECS with automatic IPv6 address assignment enabled is used to create an ECS in an environment that does not support IPv6, the ECS may start slow because of IPv6 address assignment timeout. Set the timeout duration for assigning IPv6 addresses to 30s by referring to Setting the Timeout Duration for IPv6 Address Assignment and try to create a new private image again.

enable automatic ipv6 address assignment

IPv6 is enabled for Linux public images by default, as shown in Figure 17 .

sysctl -a | grep ipv6

  • If a command output is displayed, IPv6 is enabled.
  • If no information is displayed, IPv6 is disabled. Go to 2.b to load the IPv6 module.

modprobe ipv6

net.ipv6.conf.all.disable_ipv6=0

ipv6-setup- xxx modifies the configuration file of a NIC to enable dynamic IPv6 address assignment or adds such a configuration file for a NIC, and then restarts the NIC or network service. Table 2 lists the download paths of ipv6-setup-rhel and ipv6-setup-debian .

chmod +x ipv6-setup- xxx

./ipv6-setup- xxx --dev [ dev ]

./ipv6-setup- xxx --dev eth0

  • To enable dynamic IPv6 address assignment for all NICs, run the ./ipv6-setup- xxx command.
  • To learn how to use ipv6-setup- xxx , run the ./ipv6-setup- xxx --help command.

Linux (Manually Enabling Dynamic Assignment of IPv6 Addresses)

enable automatic ipv6 address assignment

IPv6 is enabled for Linux public images by default, as shown in Figure 20 .

cd /etc/netplan

enable automatic ipv6 address assignment

vi 01-network-manager-all.yaml

enable automatic ipv6 address assignment

Save the changes and exit.

sudo netplan apply

enable automatic ipv6 address assignment

vi 01-netcfg.yaml

enable automatic ipv6 address assignment

vi /etc/NetworkManager/NetworkManager.conf

enable automatic ipv6 address assignment

systemctl restart NetworkManager

  • Add the following content to the /etc/network/interfaces file: auto lo iface lo inet loopback auto eth0 iface eth0 inet dhcp iface eth0 inet6 dhcp pre-up sleep 3
  • Add configurations for each NIC to the /etc/network/interfaces file. The following uses eth1 as an example: auto eth1 iface eth1 inet dhcp iface eth1 inet6 dhcp pre-up sleep 3

service networking restart

If no IPv6 address is assigned after the NICs are brought down and up, you can run this command to restart the network.

  • Open the configuration file /etc/sysconfig/network-scripts/ifcfg-eth0 of the primary NIC. Add the following configuration items to the file: IPV6INIT=yes DHCPV6C=yes
  • Edit the /etc/sysconfig/network file to add or modify the following line: NETWORKING_IPV6=yes

In CentOS 6.3, dhcpv6-client requests are filtered by ip6tables by default. So, you also need to add a rule allowing the dhcpv6-client request to the ip6tables file.

ip6tables -A INPUT -m state --state NEW -m udp -p udp --dport 546 -d fe80::/64 -j ACCEPT

service ip6tables save

enable automatic ipv6 address assignment

nmcli con modify " Wired connection 1 " ipv6.addr-gen-mode eui64

The NIC information varies depending on the CentOS series. In the command, Wired connection 1 needs to be replaced with the value in the NAME column of the queried NIC information.

ifdown eth1

service network restart

SUSE 11 SP4 does not support dynamic IPv6 address assignment.

No additional configuration is required for SUSE 12 SP1 or SUSE 12 SP2.

No additional configuration is required for openSUSE 13.2 or openSUSE 42.2.

No additional configuration is required for CoreOS 10.10.5.

Setting the Timeout Duration for IPv6 Address Assignment

After automatic IPv6 address assignment is configured on an ECS running CentOS 6.x or Debian, the ECS will be created as a private image. When this image is used to create an ECS in an environment that IPv6 is unavailable, the ECS may start slow because acquiring an IPv6 address times out. Before creating the private image, you can set the timeout duration for acquiring IPv6 addresses to 30s as follows:

vi /etc/dhcp/dhclient.conf

  • Press i to enter editing mode and add the timeout attribute to the file. timeout 30;
  • Enter :wq to save the settings and exit.

vi /etc/init.d/networking

enable automatic ipv6 address assignment

vi /lib/systemd/system/networking.service.d/network-pre.conf

  • Press i to enter editing mode and add the timeout attribute to the file. [Service] TimeoutStartSec=30

vi /etc/system/system/network-online.target.wants/networking.service

  • Press i to enter editing mode and change TimeoutStartSec=5min to TimeoutStartSec=30 .

Previous topic: Enabling NIC Multi-Queue

Next topic: EIPs

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Amazon EC2 instance IP addressing

Amazon EC2 and Amazon VPC support both the IPv4 and IPv6 addressing protocols. By default, Amazon VPC uses the IPv4 addressing protocol; you can't disable this behavior. When you create a VPC, you must specify an IPv4 CIDR block (a range of private IPv4 addresses). You can optionally assign an IPv6 CIDR block to your VPC and assign IPv6 addresses from that block to instances in your subnets.

Private IPv4 addresses

Public ipv4 addresses, elastic ip addresses (ipv4), ipv6 addresses, work with the ipv4 addresses for your instances, work with the ipv6 addresses for your instances.

  • Multiple IP addresses

EC2 instance hostnames

Link-local addresses.

A private IPv4 address is an IP address that's not reachable over the Internet. You can use private IPv4 addresses for communication between instances in the same VPC. For more information about the standards and specifications of private IPv4 addresses, see RFC 1918 . We allocate private IPv4 addresses to instances using DHCP.

You can create a VPC with a publicly routable CIDR block that falls outside of the private IPv4 address ranges specified in RFC 1918. However, for the purposes of this documentation, we refer to private IPv4 addresses (or 'private IP addresses') as the IP addresses that are within the IPv4 CIDR range of your VPC.

VPC subnets can be one of the following types:

IPv4-only subnets: You can only create resources in these subnets with IPv4 addresses assigned to them.

IPv6-only subnets: You can only create resources in these subnets with IPv6 addresses assigned to them.

IPv4 and IPv6 subnets: You can create resources in these subnets with either IPv4 or IPv6 addresses assigned to them.

When you launch an EC2 instance into an IPv4-only or dual stack (IPv4 and IPv6) subnet, the instance receives a primary private IP address from the IPv4 address range of the subnet. For more information, see IP addressing in the Amazon VPC User Guide . If you don't specify a primary private IP address when you launch the instance, we select an available IP address in the subnet's IPv4 range for you. Each instance has a default network interface (eth0) that is assigned the primary private IPv4 address. You can also specify additional private IPv4 addresses, known as secondary private IPv4 addresses . Unlike primary private IP addresses, secondary private IP addresses can be reassigned from one instance to another. For more information, see Multiple IP addresses .

A private IPv4 address, regardless of whether it is a primary or secondary address, remains associated with the network interface when the instance is stopped and started, or hibernated and started, and is released when the instance is terminated.

A public IP address is an IPv4 address that's reachable from the Internet. You can use public addresses for communication between your instances and the Internet.

When you launch an instance in a default VPC, we assign it a public IP address by default. When you launch an instance into a nondefault VPC, the subnet has an attribute that determines whether instances launched into that subnet receive a public IP address from the public IPv4 address pool. By default, we don't assign a public IP address to instances launched in a nondefault subnet.

You can control whether your instance receives a public IP address as follows:

Modifying the public IP addressing attribute of your subnet. For more information, see Modify the public IPv4 addressing attribute for your subnet in the Amazon VPC User Guide .

Enabling or disabling the public IP addressing feature during launch, which overrides the subnet's public IP addressing attribute. For more information, see Assign a public IPv4 address during instance launch .

A public IP address is assigned to your instance from Amazon's pool of public IPv4 addresses, and is not associated with your AWS account. When a public IP address is disassociated from your instance, it is released back into the public IPv4 address pool, and you cannot reuse it.

You cannot manually associate or disassociate a public IP (IPv4) address from your instance. Instead, in certain cases, we release the public IP address from your instance, or assign it a new one:

We release your instance's public IP address when it is stopped, hibernated, or terminated. Your stopped or hibernated instance receives a new public IP address when it is started.

We release your instance's public IP address when you associate an Elastic IP address with it. When you disassociate the Elastic IP address from your instance, it receives a new public IP address.

If the public IP address of your instance in a VPC has been released, it will not receive a new one if there is more than one network interface attached to your instance.

If your instance's public IP address is released while it has a secondary private IP address that is associated with an Elastic IP address, the instance does not receive a new public IP address.

If you require a persistent public IP address that can be associated to and from instances as you require, use an Elastic IP address instead.

If you use dynamic DNS to map an existing DNS name to a new instance's public IP address, it might take up to 24 hours for the IP address to propagate through the Internet. As a result, new instances might not receive traffic while terminated instances continue to receive requests. To solve this problem, use an Elastic IP address. You can allocate your own Elastic IP address, and associate it with your instance. For more information, see Elastic IP addresses .

AWS charges for all public IPv4 addresses, including public IPv4 addresses associated with running instances and Elastic IP addresses. For more information, see the Public IPv4 Address tab on the Amazon VPC pricing page .

Instances that access other instances through their public NAT IP address are charged for regional or Internet data transfer, depending on whether the instances are in the same Region.

An Elastic IP address is a public IPv4 address that you can allocate to your account. You can associate it to and disassociate it from instances as you require. It's allocated to your account until you choose to release it. For more information about Elastic IP addresses and how to use them, see Elastic IP addresses .

We do not support Elastic IP addresses for IPv6.

You can optionally associate an IPv6 CIDR block with your VPC and associate IPv6 CIDR blocks with your subnets. The IPv6 CIDR block for your VPC is automatically assigned from Amazon's pool of IPv6 addresses; you cannot choose the range yourself. For more information, see the following topics in the Amazon VPC User Guide :

IP addressing for your VPCs and subnets

Add an IPv6 CIDR block to your VPC

Add an IPv6 CIDR block to your subnet

IPv6 addresses are globally unique and can be configured to remain private or reachable over the Internet. Your instance receives an IPv6 address if an IPv6 CIDR block is associated with your VPC and subnet, and if one of the following is true:

Your subnet is configured to automatically assign an IPv6 address to an instance during launch. For more information, see Modify the IPv6 addressing attribute for your subnet .

You assign an IPv6 address to your instance during launch.

You assign an IPv6 address to the primary network interface of your instance after launch.

You assign an IPv6 address to a network interface in the same subnet, and attach the network interface to your instance after launch.

When your instance receives an IPv6 address during launch, the address is associated with the primary network interface (eth0) of the instance. You can manage the IPv6 addresses for your instances primary network interface (eth0) in the following ways:

Assign and unassign IPv6 addresses from the network interface. The number of IPv6 addresses you can assign to a network interface and the number of network interfaces you can attach to an instance varies per instance type. For more information, see IP addresses per network interface per instance type .

Enable a primary IPv6 address. A primary IPv6 address enables you to avoid disrupting traffic to instances or ENIs. For more information, see Create a network interface or Manage IP addresses .

An IPv6 address persists when you stop and start, or hibernate and start, your instance, and is released when you terminate your instance. You cannot reassign an IPv6 address while it's assigned to another network interface—you must first unassign it.

You can control whether instances are reachable via their IPv6 addresses by controlling the routing for your subnet or by using security group and network ACL rules. For more information, see Internetwork traffic privacy in the Amazon VPC User Guide .

For more information about reserved IPv6 address ranges, see IANA IPv6 Special-Purpose Address Registry and RFC4291 .

You can assign a public IPv4 address to your instance when you launch it. You can view the IPv4 addresses for your instance in the console through either the Instances page or the Network Interfaces page.

View the IPv4 addresses

Assign a public ipv4 address during instance launch.

You can use the Amazon EC2 console to view the public and private IPv4 addresses of your instances. You can also determine the public IPv4 and private IPv4 addresses of your instance from within your instance by using instance metadata. For more information, see Instance metadata and user data .

The public IPv4 address is displayed as a property of the network interface in the console, but it's mapped to the primary private IPv4 address through NAT. Therefore, if you inspect the properties of your network interface on your instance, for example, through ifconfig (Linux) or ipconfig (Windows), the public IPv4 address is not displayed. To determine your instance's public IPv4 address from an instance, use instance metadata.

To view the IPv4 addresses for an instance using the console

Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/ .

In the navigation pane, choose Instances and select your instance.

The following information is available on the Networking tab:

Public IPv4 address — The public IPv4 address. If you associated an Elastic IP address with the instance or the primary network interface, this is the Elastic IP address.

Private IPv4 addresses — The private IPv4 address.

Secondary private IPv4 addresses — Any secondary private IPv4 addresses.

To view more detailed information, on the Networking tab, choose the ID of the primary network interface to open the Network interfaces page, and then choose the ID of the network interface to open its details page.

To view the IPv4 addresses for an instance using the command line

You can use one of the following commands. For more information about these command line interfaces, see Access Amazon EC2 .

describe-instances (AWS CLI)

Get-EC2Instance (AWS Tools for Windows PowerShell).

To determine your instance's IPv4 addresses using instance metadata

Connect to your instance. For more information, see Connect to your Linux instance .

Use the following command to access the private IP address:

Use the following command to access the public IP address:

If an Elastic IP address is associated with the instance, the value returned is that of the Elastic IP address.

Each subnet has an attribute that determines whether instances launched into that subnet are assigned a public IP address. By default, nondefault subnets have this attribute set to false, and default subnets have this attribute set to true. When you launch an instance, a public IPv4 addressing feature is also available for you to control whether your instance is assigned a public IPv4 address; you can override the default behavior of the subnet's IP addressing attribute. The public IPv4 address is assigned from Amazon's pool of public IPv4 addresses, and is assigned to the network interface with the device index of eth0. This feature depends on certain conditions at the time you launch your instance.

Considerations

You can't manually disassociate the public IP address from your instance after launch. Instead, it's automatically released in certain cases, after which you cannot reuse it. For more information, see Public IPv4 addresses . If you require a persistent public IP address that you can associate or disassociate at will, assign an Elastic IP address to the instance after launch instead. For more information, see Elastic IP addresses .

You cannot auto-assign a public IP address if you specify more than one network interface. Additionally, you cannot override the subnet setting using the auto-assign public IP feature if you specify an existing network interface for eth0.

The public IP addressing feature is only available during launch. However, whether you assign a public IP address to your instance during launch or not, you can associate an Elastic IP address with your instance after it's launched. For more information, see Elastic IP addresses . You can also modify your subnet's public IPv4 addressing behavior. For more information, see Modify the public IPv4 addressing attribute for your subnet .

To assign a public IPv4 address during instance launch using the console

Follow the procedure to launch an instance , and when you configure Network Settings , choose the option to Auto-assign Public IP .

To enable or disable the public IP addressing feature using the command line

Use the --associate-public-ip-address or the --no-associate-public-ip-address option with the run-instances command (AWS CLI)

Use the -AssociatePublicIp parameter with the New-EC2Instance command (AWS Tools for Windows PowerShell)

You can view the IPv6 addresses assigned to your instance, assign a public IPv6 address to your instance, or unassign an IPv6 address from your instance. You can view these addresses in the console through either the Instances page or the Network Interfaces page.

View the IPv6 addresses

Assign an ipv6 address to an instance, unassign an ipv6 address from an instance.

You can use the Amazon EC2 console, AWS CLI, and instance metadata to view the IPv6 addresses for your instances.

To view the IPv6 addresses for an instance using the console

In the navigation pane, choose Instances .

Select the instance.

On the Networking tab, locate IPv6 addresses .

To view the IPv6 addresses for an instance using the command line

To view the ipv6 addresses for an instance using instance metadata.

Use the following command to view the IPv6 address (you can get the MAC address from http://169.254.169.254/latest/meta-data/network/interfaces/macs/ ).

If your VPC and subnet have IPv6 CIDR blocks associated with them, you can assign an IPv6 address to your instance during or after launch. The IPv6 address is assigned from the IPv6 address range of the subnet, and is assigned to the network interface with the device index of eth0.

To assign an IPv6 address during instance launch

Follow the procedure to launch an instance , and when you configure Network Settings , choose the option to Auto-assign IPv6 IP .

To assign an IPv6 address after launch

Select your instance, and choose Actions , Networking , Manage IP addresses .

Expand the network interface. Under IPv6 addresses , choose Assign new IP address . Enter an IPv6 address from the range of the subnet or leave the field blank to let Amazon choose an IPv6 address for you.

Choose Save .

To assign an IPv6 address using the command line

Use the --ipv6-addresses option with the run-instances command (AWS CLI)

Use the Ipv6Addresses property for -NetworkInterface in the New-EC2Instance command (AWS Tools for Windows PowerShell)

assign-ipv6-addresses (AWS CLI)

Register-EC2Ipv6AddressList (AWS Tools for Windows PowerShell)

You can unassign an IPv6 address from an instance at any time.

To unassign an IPv6 address from an instance using the console

Expand the network interface. Under IPv6 addresses , choose Unassign next to the IPv6 address.

To unassign an IPv6 address from an instance using the command line

unassign-ipv6-addresses (AWS CLI)

Unregister-EC2Ipv6AddressList (AWS Tools for Windows PowerShell).

When you create an EC2 instance, AWS creates a hostname for that instance. For more information on the types of hostnames and how they're provisioned by AWS, see Amazon EC2 instance hostname types . Amazon provides a DNS server that resolves Amazon-provided hostnames to IPv4 and IPv6 addresses. The Amazon DNS server is located at the base of your VPC network range plus two. For more information, see DNS attributes for your VPC in the Amazon VPC User Guide .

Link-local addresses are well-known, non-routable IP addresses. Amazon EC2 uses addresses from the link-local address space to provide services that are accessible only from an EC2 instance. These services do not run on the instance, they run on the underlying host. When you access the link-local addresses for these services, you're communicating with either the Xen hypervisor or the Nitro controller.

Link-local address ranges

IPv4 – 169.254.0.0/16 (169.254.0.0 to 169.254.255.255)

IPv6 – fe80::/10

Services that you access using link-local addresses

Instance Metadata Service

Amazon Route 53 Resolver (also known as the Amazon DNS server)

Amazon Time Sync Service

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Catalyst 1200 Admin Guide

Bias-free language.

The documentation set for this product strives to use bias-free language. For the purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. Learn more about how Cisco is using Inclusive Language.

  • Get To Know Your Switch
  • Getting Started
  • Configuration Wizards
  • Status and Statistics
  • Administration
  • Port Management
  • VLAN Management
  • Spanning Tree
  • MAC Address Tables
  • IPv4 Configuration

IPv6 Configuration

  • General IP Configuration
  • Access Control
  • Quality of Service

Clear Contents of Search

Chapter: IPv6 Configuration

Ipv6 global configuration, ipv6 interfaces, ipv6 tunnels, ipv6 addresses, router advertisement, ipv6 prefixes, ipv6 default router list, ipv6 neighbors, ipv6 routes, global destinations, interface settings.

This chapter contains the following sections:

The Internet Protocol version 6 (IPv6) is a network-layer protocol for packet-switched internet works. IPv6 was designed to replace IPv4, the predominantly deployed Internet protocol. IPv6 introduces greater flexibility in assigning IP addresses, because the address size increases from 32-bit to 128-bit addresses. IPv6 addresses are written as eight groups of four hexadecimal digits, for example FE80:0000:0000:0000:0000:9C00:876A:130B. The abbreviated form, in which a group of zeroes can be left out, and replaced with '::', is also acceptable, for example, FE80::9C00:876A:130B. IPv6 interface addresses can be configured manually by the user, or automatically configured by a DHCP server.

This section provides information for defining the device IPv6 addresses, either manually or by making the device a DHCP client. To define IPv6 global parameters and DHCPv6 client settings, follow these steps:

The Internet Protocol version 6 (IPv6) is a network-layer protocol used for packet-switched internet communications.IPv6 was created to replace IPv4, the most widely used Internet protocol. Because the address size increases from 32-bit to 128-bit, IPv6 allows for greater flexibility in assigning IP addresses. IPv6 addresses are composed of eight groups of four hexadecimal digits, such as FE80:0000:0000:0000:0000:9C00:876A:130B.

To communicate with other IPv6 nodes over an IPv4-only network, IPv6 nodes require an intermediary mapping mechanism. This mechanism, known as a tunnel, allows IPv6-only hosts to access IPv4 services and isolated IPv6 hosts and networks to connect to an IPv6 node via the IPv4 infrastructure.

An IPv6 interface can be configured on a port, LAG, VLAN, loopback interface or tunnel. To define an IPv6 interface, follow these steps:

To define an IPv6 interface, follow these steps:

Tunnels enable transmission of IPv6 packets over IPv4 networks. Each tunnel has a source IPv4 address and if it’s a manual tunnel it also has a destination IPv4 address. The IPv6 packet is encapsulated between these addresses.

The device supports a single Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) tunnel. An ISATAP tunnel is a point-to-multi-point tunnel. The source address is the IPv4 address (or one of the IPv4 addresses) of the device. When configuring an ISATAP tunnel, the destination IPv4 address is provided by the router. Note that:

An IPv6 link local address is assigned to the ISATAP interface. The initial IP address is assigned to the interface, which is then activated.

If an ISATAP interface is active, the ISATAP router IPv4 address is resolved via DNS by using ISATAP-to-IPv4 mapping. If the ISATAP DNS record is not resolved, ISATAP host name-to-address mapping is searched in the host mapping table

When the ISATAP router IPv4 address is not resolved via the DNS process, the ISATAP IP interface remains active. The system does not have a default router for ISATAP traffic until the DNS process is resolved.

To configure an IPv6 tunnel follow these steps:

To assign an IPv6 address to an IPv6 Interface, follow these steps:

IPv6 Address

In addition to the default link local and Multicast addresses, the device also automatically adds global addresses to the interface based on the router advertisements it receives. The device supports a maximum of 128 addresses at the interface. Each address must be a valid IPv6 address that is specified in hexadecimal format by using 16-bit values separated by colons.

Prefix Length

The length of the Global IPv6 prefix is a value from 3-128 indicating the number of the high-order contiguous bits of the address comprise the prefix (the network portion of the address).

Select Enable to use the EUI-64 parameter to identify the interface ID portion of the Global IPv6 address by using the EUI-64 format based on a device MAC address.

Step 5

Click Apply . The Running Configuration file is updated.

IPv6 Router Configuration

The following sections describe how to configure IPv6 routers. It covers the following topics:

A router advertisement packet contains various configurations for IPv6 hosts including the network part of the layer 3 IPv6 address required by hosts to communicate in the internet. Clients then generate the universally unique host part of the address and derive the complete address. This feature can be enabled or suppressed per interface, as follows:

Neighbor Solicitation Retransmissions Interval

Enter the interval to determine the time between retransmissions of neighbor solicitation messages to a neighbor when resolving the address or when probing the reachability of a neighbor (User Defined), or select Use Default to use the system default (1000).

Maximum Router Advertisement Interval

Enter the maximum amount of time that can pass between router advertisements.

The interval between transmissions should be less than or equal to the IPv6 router advertisement lifetime if you configure the route as a default router by using this command. To prevent synchronization with other IPv6 nodes, the actual interval used is randomly selected from a value between the minimum and maximum values.

Minimum Router Advertisement Interval

Enter the minimum amount of time that can pass between router advertisements (User Defined) or select Use Default to user the system default.

Router Advertisement Lifetime

Enter the remaining length of time, in seconds, that this router remains useful as a default router. A value of zero indicates that it’s no longer useful as a default router.

Reachable Time

Enter the amount of time that a remote IPv6 node is considered reachable (in milliseconds) (User Defined) or select the Use Default option to use the system default.

Step 4

Click Apply to save the configuration to the Running Configuration file.

To define prefixes to be advertised on the interfaces of the device, follow these steps:

Step 6

The IPv6 Default Router List page enables configuring and viewing the default IPv6 router addresses. This list contains the routers that are candidates to become the device default router for non-local traffic (it may be empty). The device randomly selects a router from the list. The device supports one static IPv6 default router. Dynamic default routers are routers that have sent router advertisements to the device IPv6 interface.

When adding or deleting IP addresses, the following events occur:

When removing an IP interface, all the default router IP addresses are removed. Dynamic IP addresses can’t be removed.

An alert message appears after an attempt is made to insert more than a single user-defined address.

An alert message appears when attempting to insert a non-link local type address, meaning 'fe80:'.

To define a default router, complete the following:

The IPv6 Neighbors page enables configuring and viewing the list of IPv6 neighbors on the IPv6 interface. The IPv6 Neighbor Table (also known as IPv6 Neighbor Discovery Cache) displays the MAC addresses of the IPv6 neighbors that are in the same IPv6 subnet as the device. This is the IPv6 equivalent of the IPv4 ARP Table. When the device needs to communicate with its neighbors, the device uses the IPv6 Neighbor Table to determine the MAC addresses based on their IPv6 addresses.

This page displays the neighbors that automatically detected or manually configured entries. Each entry displays to which interface the neighbor is connected, the neighbor’s IPv6 and MAC addresses, the entry type (static or dynamic), and the state of the neighbor.

To define IPv6 neighbors, complete the following steps:

The IPv6 Forwarding Table contains the various routes that have been configured. One of these routes is a default route (IPv6 address: 0) that uses the default router selected from the IPv6 Default Router List to send packets to destination devices that aren’t in the same IPv6 subnet as the device. In addition to the default route, the table also contains dynamic routes that are ICMP redirect routes received from IPv6 routers by using ICMP redirect messages. This could happen when the default router the device uses isn’t the router for traffic to which the IPv6 subnets that the device wants to communicate.

To view IPv6 routes:

Click IPv6 Configuration > IPv6 Routes .

This page displays the following fields:

IPv6 Prefix—IP route address prefix for the destination IPv6 subnet address

Prefix Length—IP route prefix length for the destination IPv6 subnet address It’s preceded by a forward slash.

Next Hop—Type of address to which the packet is forwarded. Typically, this is the address of a neighboring router. It can be one of the following types.

Link Local—An IPv6 interface and IPv6 address that uniquely identifies hosts on a single network link. A link local address has a prefix of FE80, isn’t routable, and can be used for communication only on the local network. Only one link local address is supported. If a link local address exists on the interface, this entry replaces the address in the configuration.

Global—An IPv6 address that is a global Unicast IPV6 type that is visible and reachable from other networks.

Outgoing Interface—Interface used to forward the packet.

Metric—Value used for comparing this route to other routes with the same destination in the IPv6 router table All default routes have the same value.

Lifetime—Time period during which the packet can be sent, and resent, before being deleted.

Route Type—How the destination is attached, and the method used to obtain the entry. The following values are:

S (Static)—Entry was manually configured by a user.

I (ICMP Redirect)—Entry is an ICMP redirect dynamic route received from an IPv6 router by using ICMP redirect messages.

ND (Router Advertisement)—Entry is taken from a router advertisement message.

DHCPv6 Relay

DHCPv6 Relay is used for relaying DHCPv6 messages to DHCPv6 servers. It’s defined in RFC 3315.

When the DHCPv6 client isn’t directly connected to the DHCPv6 server, a DHCPv6 relay agent (the device) to which this DHCPv6 client is directly-connected encapsulates the received messages from the directly connected DHCPv6 client, and forwards them to the DHCPv6 server.

In the opposite direction, the relay agent decapsulates packets received from the DHCPv6 server and forwards them, towards the DHCPv6 client.

The user must configure the list DHCP servers to which packets are forwarded. Two sets of DHCPv6 servers can be configured:

Global Destinations—Packets are always relayed to these DHCPv6 servers.

Interface List—This is a per-interface list of DHCPv6 servers. When a DHCPv6 packet is received on an interface, the packet is relayed both to the servers on the interface list (if it exists) and to the servers on the global destination list.

To configure a list of DHCPv6 servers to which all DHCPv6 packets are relayed, complete the following steps:

To enable the DHCPv6 Relay feature on an interface and to configure a list of DHCPv6 servers, follow these steps:

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How can I figure out what IPv6 to use if I want to set a static IP for my computer?

I recently installed Windows Server 2012 on my desktop. I changed my connection settings to hardcode my internal IP address as 192.168.0.99 (IPv4). Windows Server 2012 warned me that I should also set my IPv6 address to a static address, but I'm not sure what the equivalent address is in IPv6 format. I've attempted to google this, however after visiting a few websites that "convert IPv4 to IPv6" they each give me different values. I'm not sure which one is the correct one.

How does one go about translating an IPv4 address to and IPv6 address appropriately? Specifically, I'd like to know what 192.168.0.99 is in IPv6 format. Thanks!

  • windows-server-2012

BatchyX's user avatar

  • Tell your OS to use unique local addresses. These are the real replacement for private addresses. They cannot be fixed, because they have to be unique even when LAN are merged, but under normal condition, they should stay the same if there is no conflict. –  BatchyX Jan 5, 2013 at 13:28
  • 2 the 192.168.*.* * (reusable/unrouted addresses) addresses are a work around for ipv4 to be able to continue to work while running out of address space. ipv6 is the solution. –  ctrl-alt-delor Jan 5, 2013 at 14:25

5 Answers 5

IPv6 has an equivalent of IPv4 "private range" addresses – called Unique Local Address ( RFC 4193 ) – it uses the fd00::/8 range. Pick a random /48 or /64 prefix within that range (see Wikipedia article for examples) and use it for your network.

A direct translation of your internal IPv4 addresses wouldn't make much sense, however. (If you did that, you'd also have the same limits as with IPv4, don't you think?)

However, with IPv6 it is not necessary to use local addresses. There are several ways you can get a global address range for yourself, even if your ISP doesn't offer native IPv6 yet:

You can sign up at Tunnelbroker or similar services; most of them will give you a globally-reachable /64 block – that's one subnet – and many will even provide /48 or /56 blocks upon request (64k and 256 subnets respectively). The same tunnel also lets you access the global IPv6 internet.

Or you can use the 6to4 address range based on your global IP address. For example, if your ISP assigns you 192.0.123.234 (C0 00 7B EA in hexadecimal), then you're allowed to use 2002:c000:7bea::/48 . Such addresses are reachable from the Internet as well.

Community's user avatar

  • Good advise. If you want to run IPv6 on your LAN this is the way to do it. –  Sander Steffann Jan 6, 2013 at 14:23

To expand grawity's answer (the equivalent to private ranges are Unique Local Addresses, RFC 4913), here is how to pick the actual address to use.

With IPv4 private ranges like 192.168.X. , you randomly pick the value for X, but only get a few values to choose from (you picked 192.168.0. ), and then pick a random number for the machine (you picked 99). You can have multiple networks, e.g. 192.168.1. , but can't really combine two existing sets of networks together as they will likely clash. Using the private range 10.X.Y. gives you more options, but is still limited.

With IPv6, start with 'fd', followed by ten hex digits for your unique allocation (x), and four hex digits for your network (y). Each machine then have a number up to 16 hex digits (z).

This will give you a value like 'fdxx:xxxx:xxxx:yyyy:zzzz:zzzz:zzzz:zzzz', although if you put a lot of zeros in it will be a lot shorter to write out.

e.g. Pick '12:3456:789a' as your first random ten (x), and then use network '0001' inside that (y), then for your machine pick '0000:0000:0000:0063' (because hex 63 is the same as decimal 99).

This would give your machine the IPv6 address 'fd12:3456:789a:0001:0000:0000:0000:0063'. (For your specific network use different, random, values for the 12:3456:789a part.)

As you can collapse zeros in shorthand notation, this becomes just 'fd12:3456:789a:1::63'.

Your entire allocation would be 'fd12:3456:789a::/48', and subnet you are using would be 'fd12:3456:789a:1::/64'.

Note that the above examples happen to have the same number (99 decimal, 0x0063 hex) for the machine in both the IPv4 and IPv6 ranges, but they don't have to match (it just might be easier).

Sly Gryphon's user avatar

Firstly, there is no use in using a IPv6 address on a home network but still if you want to you then you should set it to automatic (just for IPv6), also your router must support DHCPv6 or Windows server will convert IPv4 to IPv6 automatically. As you want to try out into for static IPv6 Address then...

There are multiple types of IPv6 addresses that can be used, frankly speaking, even I don't know about them all. Below is a conversion table for the IPv4 specified. This is one of the best tool I can trust.

Conversion Table

As far as I can say, you should use 2002:C0A8:63:0:0:0:0:0 as your static IPv6 Address. (I was using another format earlier but someone commented that the format should never be used on wire. I have myself switched to this format now.)

There is a similar ServerFault Question , I think this would help you a bit.

Akshat Mittal's user avatar

  • 2 Addresses link 0:0:0:0:0:ffff:c0a8:0063 are so that software can use the IPv6 APIs even when communicating over IPv4. They must never be used on the wire (and therefor also not as an interface address)! –  Sander Steffann Jan 6, 2013 at 14:22
  • Okay, I have changed the IPv6 to 2002:C0A8:63:0:0:0:0:0 , its the 6-to-4 format –  Akshat Mittal Jan 7, 2013 at 10:47

Yes if you are using NAT you don't have to move to IPv6 but 1) NAT is problematic, especially for Voice over IP services 2) NAT does not allow for incoming connections without setuo for each incoming connection and even then you are limited 3) NAT adds complication and increases routing time/effort

To answer the actual question asked you can encode an IPv4 address into an IPv6 address in the form ::FFFF:

So the IPv4 address of 119.225.152.21 can be represented in IPv6 as 0:0:0:0:0:FFFF:119.225.152.21 which is abreviated to ::FFFF:192.225.152.21

each section of the IPv4 address will be sent in Hex of course so a network trace will show ::FFFF:C0E1:9815 as 192=C0 in hex, 225=E1,152=98 in hex etc

This will be converted to the IPv4 address when leaving an IPv6 network and entering an IPv4 network

See this page has some info on this

http://computernetworkingnotes.com/ipv6-features-concepts-and-configurations/special-ipv6-to-devices.html

rms-mit's user avatar

There is no real need and probably no point to setting an IPv6 address on your internal network. Just stick with the IPv4 address and ignore the warning. The warning would be relevant for use on a public server so unless you have good reason for running IPv6 on your internal network I wouldn't worry about it.

On your other point, there is no IPv6 'translation' of an IPv4 address. They are separate systems.

In order to assign an IPv6 on your desktop, you would need to configure your internal router to manage an IPv6 network.

If you did want to run a home IPv6 network, then there are some helpful comments in the following questions:

  • Is there any benefit to using IPv6 on my home network?
  • How will home networks work in the IPv6 world?

harunahi's user avatar

  • 9 I'd still like to, for correctness, even if it is optional. –  myermian Jan 5, 2013 at 13:19
  • You would need to also configure your router for IPv6 if you wanted to run an IPv6 network internally. There are some useful comments here: superuser.com/questions/43853/… –  harunahi Jan 5, 2013 at 13:29
  • 1 IPv6 is used in a lot more places than you think. Every interface has a link-local IPv6 address by default these days. Setting a global IPv6 address is usually only useful when your ISP provides it to you, but you can run a local IPv6 network using ULA (Unique Local Addresses). –  Sander Steffann Jan 6, 2013 at 14:20
  • 7 This was a mediocre answer in 2013; today it's dangerously out of date. –  Michael Hampton Mar 11, 2017 at 23:21

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  2. How to Enable & Assign IPv6 Address in DirectAdmin

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  3. How-to: IPv6 address planning

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  4. IPv6 Stateless Address Auto-configuration (SLAAC)

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  5. Manipulate IPv6 Addresses with ipv6calc

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  6. Assigning IPv6 Addresses

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VIDEO

  1. FEATURES OF IPv6

  2. Understanding IPv4 Addressing

  3. IPv4 vs IPv6 IP Addresses

  4. Enable/Disable TCP/IPv6 on Windows 11

  5. Router IPv6 Configuration

  6. 12.3

COMMENTS

  1. IPv6 Stateless Address Auto-configuration (SLAAC)

    What is SLAAC? SLAAC stands for Stateless Address Autoconfiguration and the name pretty much explains what it does. It is a mechanism that enables each host on the network to auto-configure a unique IPv6 address without any device keeping track of which address is assigned to which node.

  2. Dynamic address assignment in IPv6 using SLAAC and DHCP

    The DHCP server keeps a record of all clients and the IPv6 address assigned to them. Below is a configuration example of a server and client using stateful DHCP. Server configuration: ipv6 dhcp pool IPV6_DHCPPOOL. address prefix 2001:DB8:1000::/64 lifetime infinite infinite. link-address 2001:DB8:1000::1/64.

  3. IPv6 Addressing and Basic Connectivity Configuration Guide ...

    Updated: March 19, 2015 Chapter: IPv6 Addressing and Basic Connectivity Chapter Contents Internet Protocol version 6 (IPv6) expands the number of network address bits from 32 bits (in IPv4) to 128 bits, which provides more than enough globally unique IP addresses for every networked device on the planet.

  4. IPv6: How to configure static and DHCP IP addressing and deal with DNS

    In Settings go to Network & Internet and click the Properties button for the interface you wish to configure. Click the Edit button under IP settings, change the configuration type to Manual,...

  5. Troubleshoot IPv6 Dynamic Address Assignment with Cisco Router and

    Introduction This document describes the available options for dynamic IPv6 address assignment. Troubleshoot of Stateless Address Autoconfiguration (SLAAC) and Dynamic Host Configuration Protocol version 6 (DHCPv6) are covered. Prerequisites Requirements Cisco recommends that you have knowledge of these topics: IPv6 address architecture

  6. IPv6 Dynamic Address Allocation Mechanism Illustrated

    The interface identifier can be generated in several ways: Static manual setting Converted from the interface's MAC address using the modified EUI-64 format Obtained from a DHCPv6 server Automatically established randomly or cryptographically IETF recommends a canonical textual representation format for ease of writing.

  7. IPv6 Configuration Guide, Cisco IOS Release 15.0S

    To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required. Restrictions for Implementing DHCP for IPv6 Cisco IOS Release 12.0S provides IPv6 support on Gigabit Switch Routers (GSRs) and Cisco 10720 Internet routers only.

  8. IPv6 Address Assignment Example

    Where do we start? Take a look at the image below: The 48-bit prefix that we received is typically called the global routing prefix or site prefix. The interface ID is normally 64 bit which means we have 16 bits left to create subnets.

  9. IPv6 address assignment

    IPv6 addresses can be assigned to an interface by doing the following: Manually configuring one or more IPv6 addresses on the interface Stateful address autoconfiguration using a DHCPv6 server Stateless address autoconfiguration based on the receipt of Router Advertisement messages Both stateful and stateless address autoconfiguration

  10. How do I assign IPv6 addresses manually?

    Ask Question Asked 4 years, 5 months ago Modified 4 years, 5 months ago Viewed 22k times 3 So I'm still rather clueless with IPv6, but I wanted to try something with my network today. Currently, I assign IPv4 LAN addresses manually, so that my router is 192.168..1, then my first computer is 192.168..2, and so on.

  11. Configuring IPv6 address autoconfiguration

    You can configure a line description to perform IPv6 address autoconfiguration using either a wizard in System i® Navigator, or the character-based interface. In System i Navigator, expand your system > Network > TCP/IP Configuration > Lines. > Configure. Follow the steps in the New IPv6 Interface wizard to complete the autoconfiguration. > Start.

  12. Network Component: IPv6 Address Assignment

    The IPv6 addresses for the Ethernet network interface are assigned in several ways: Static IPv6. The IPv6 address, subnet prefix length and default gateway are configured manually in the system configuration file. However, it is possible to change the IPv6 address at runtime. The static configuration specifies also a primary and optional ...

  13. 9 Steps

    In this configuration lesson, we will follow the below IPv6 Configuration steps: Enable IPv6 Globally. Enable IPv6 on Interface. Configure EUI-64 Format Global Unicast Address. Configure Manual Global Unicast Address. IPv6 Ping. Manual Link Local Address Configuration. Auto IPv6 Address Configuration.

  14. IP addressing for your VPCs and subnets

    Use Amazon VPC IP Address Manager VPC CIDR blocks Subnet CIDR blocks Managed prefix lists AWS IP address ranges Migrate from IPv4 to IPv6 IPv6 support on AWS Compare IPv4 and IPv6 The following table summarizes the differences between IPv4 and IPv6 in Amazon EC2 and Amazon VPC.

  15. Configuring IPv6 Client IP Address Learning

    Enabling IPv6 on a Interface and Providing IPv6 Addresses to DHCP Clients Configuring IPv6 Client IP Address Learning Prerequisites for IPv6 Client Address Learning Before configuring IPv6 client address learning, configure the wireless clients to support IPv6. Information About IPv6 Client Address Learning

  16. Dynamically Assigning IPv6 Addresses

    Linux: Dynamic assignment of IPv6 addresses can be enabled automatically (recommended) or manually. If a private image created from a CentOS 6.x or Debian ECS with automatic IPv6 address assignment enabled is used to create an ECS in an environment that does not support IPv6, the ECS may start slow because of IPv6 address assignment timeout.

  17. Amazon EC2 instance IP addressing

    The IPv6 address is assigned from the IPv6 address range of the subnet, and is assigned to the network interface with the device index of eth0. To assign an IPv6 address during instance launch. Follow the procedure to launch an instance, and when you configure Network Settings, choose the option to Auto-assign IPv6 IP.

  18. Enable or disable the Automatic IPv6 Address Assignment

    If Enable DHCP-PD is enabled in the previous LAN IPv6 Address Settings: Enable Automatic Enable or disable DHCP-PD for other IPv6 routers connected DHCP-PD in LAN to the LAN interface. Autoconfiguration Select SLAAC+RDNSS, SLAAC+Stateless DHCP, or Stateful Type DHCPv6. If you selected SLAAC+RDNSS or SLAAC+Stateless DHCP as the Autoconfiguration ...

  19. How to Enable IPv6 on a Cisco Router?

    First, enable IPv6 routing on a Cisco router using the 'ipv6 unicast-routing' global configuration command. This command globally enables IPv6 and must be the first command executed on the router. Configure the IPv6 global unicast address on an interface using the 'ipv6 address address/prefix-length [eui-64]' command.

  20. Cisco ASA: IPv6 Quick Start

    There are 2 ways to assign a link local address to the interface. Step 1.1. Configure the interface to generate a link local address from its MAC address. interface GigabitEthernet 0/0 no shutdown nameif inside ipv6 enable. When you enter IPv6 enable, a link local address is automatically generated (this is based on your mac address). Step 1.2.

  21. Catalyst 1200 Admin Guide

    IPv6 Address Auto Configuration—Select Enable to enable automatic address configuration from router advertisements sent by neighbors. Number of DAD Attempts—Enter the number of consecutive neighbor solicitation messages that are sent while Duplicate Address Detection (DAD) is performed on the interface's Unicast IPv6 addresses.

  22. networking

    IPv6 has an equivalent of IPv4 "private range" addresses - called Unique Local Address - it uses the fd00::/8 range. Pick a random /48 or /64 prefix within that range (see Wikipedia article for examples) and use it for your network.. A direct translation of your internal IPv4 addresses wouldn't make much sense, however.

  23. Subnets must not automatically assign public IP addresses

    Auto-assigning a public IPv4/IPv6 address to your VPC subnet could expose the new EC2 instances deployed within the subnet to the Internet, and this can increase the attack surface. Because not all Amazon EC2 instances have to be publicly reachable, you should avoid direct exposure to the Internet by disabling the auto-assign public IP address ...