cannot assign requested address) while connecting to upstream client

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The Basics of Pulling an IP Address: What You Need to Know

When it comes to understanding the internet, knowing how to pull an IP address is a fundamental skill. An IP address (Internet Protocol address) is a unique identifier that is assigned to each device connected to the internet. It is used to identify and locate a device on the network, enabling communication between two or more devices. In this article, we will discuss the basics of pulling an IP address, including what it is, why it’s important, and how to do it.

What is an IP Address?

An IP address is a numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication. It uniquely identifies each device on the network and allows data packets to be routed from one device to another. An IP address consists of four numbers separated by periods, such as 192.168.1.1.

Why is Pulling an IP Address Important?

Pulling an IP address can be useful in many situations. For example, if you are troubleshooting a network issue or trying to track down malicious activity on your network, you may need to pull an IP address in order to identify the source of the problem or determine which device is responsible for the malicious activity. Additionally, if you are trying to access a website or service that requires authentication, you may need to pull your own IP address in order to gain access.

How Do You Pull an IP Address?

Pulling an IP address can be done in several ways depending on your operating system and what type of information you need. On Windows systems, you can use the ipconfig command in Command Prompt or PowerShell; on Mac systems, you can use the ifconfig command in Terminal; and on Linux systems, you can use the ip command in Terminal. Additionally, there are websites that allow you to look up your public IP address without having to run any commands or install any software.

In conclusion, knowing how to pull an IP address is essential for understanding how networks work and troubleshooting any issues that may arise with them. With this knowledge in hand, you’ll be able to identify devices on your network and access services that require authentication with ease.

This text was generated using a large language model, and select text has been reviewed and moderated for purposes such as readability.

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failed (99: Cannot assign requested address) while connecting to upstream, #938

Shreewebs commented Sep 29, 2018

mofolo commented Jan 8, 2019

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fevangelou commented Jan 22, 2019

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Nginx: Cannot assign requested address for upstream

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A few days ago, I ran into the following interesting Nginx error message.

My configuration was very simple. This was an Nginx proxy that did all the SSL encryption and sent traffic to a Varnish instance, running on port :80 on localhost. The big takeway here is that it was a pretty high traffic Nginx proxy.

Even with keepalive enabled in the nginx upstream , the error popped up. But what did it mean?

TCP ports and limits

It’s good to know a thing or two about networking besides just servers once in a while. The problem occurred because the server couldn’t get a free TCP port quickly enough to make the connection to 127.0.0.1 .

The ss tool gives you stats on the sockets/ports on the server. In this case, I had 51.582 TCP sessions in use (either active, closed, awaiting to be closed, …).

A normal server has around 28.000 possible TCP ports it can use to make a TCP connection to a remote (or local) system. Everything that talks via an IP address will pick a free port from this range to serve as source port for the outgoing connection. This port range is defined by the ip_local_port_range sysctl parameter.

The format is “ minimum maximum ” port. So 61000 – 32768 = 28 232 available source ports.

An nginx SSL proxy that connects to a Varnish instance running on localhost will look like this in your netstat .

The key takeaways here the source connection 127.0.0.1:37713 that connects to its endpoint 127.0.0.1:80 . For every source connection a new TCP source port is selected from the range in the ip_local_port_range parameter.

The combination of a source IP, source port, destination IP and destination IP needs to be unique. This is what’s called a quadruplet in networking terms. You likely can’t (easily) change the source IP. The source port is dynamically picked. That only leaves the destination IP and the destination port that are free to play with.

Solving the source port limitation

There are a couple of easy fixes. First, the ip_local_port_range can be increased on a Linux machine (for more reading material, see increase ip_local_port_range TCP port range in Linux ).

This effectively increases the total port range from its default 28 232 ports to 49 000 ports.

If that’s not enough, you can add more destination IPs to connect to. Remember that each connection consists of the 4 parts (called quadruplets ) with source IP and source port, destination IP and destination port. If you can’t change the source port or IP, just change the destination IPs.

Consider this kind of upstream definition in Nginx;

Such a definition can be used in your nginx configurations with the proxy_pass directive.

Now if you know that each server usually has 2 IPs or more, it’s very easy to add more quadruplets to your networking stack by adding an addition IP to your Nginx upstream. You’ve already added 127.0.0.1 , but your server will have another IP (its public or DHCP IP) that you can safely add too, if your webserver binds to all ports.

Every IP you add in your upstream is effectively adding 49.000 local ports to your networking stack. You can even add non-routable local IPs to your server, as interface aliases , just to use as new destination IPs for your proxy configurations.

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Nginx proxy: connect() to ip:80 failed (99: Cannot assign requested address)

An nginx/1.0.12 running as a proxy on Debian 6.0.1 starts throwing the following error after running for a short time:

Not all requests produce this error, so I suspect that it has to do with the load of the server and some kind of limit it hit.

I have tried raising ulimit -n to 50k and worker_rlimit_nofile to 50k as well, but that does not seem to help. lsof -n shows a total of 1200 lines for nginx. Is there a system limit on outgoing connections that might prevent nginx from opening more connections to its upstream server?

Best Solution

Seems like I just found the solution to my own question: Allocating more outgoing ports via

solved the problem.

Related Solutions

Nginx 1.2.0 – socket.io – http/1.1 – proxy websocket connections.

No, this is not yet possible; nginx 1.2 incorporates stuff from the 1.1.x development branch which indeed includes HTTP/1.1 reverse proxying. Websocket connections are established using the HTTP/1.1 "Upgrade" header, but the fact that nginx now supports this kind of headers does not mean it supports websockets (websockets are a different protocol, not HTTP). (I tried this myself using the 1.1.x branch (which I found to be stable enough for my purpose) and it doesn't work without the tcp_module)

Websockets will probably be supported in 1.3.x ( http://trac.nginx.org/nginx/roadmap ).

Your alternatives are:

• keep using node-http-proxy
• use nginx without tcp module; socket.io won't use websockets but something else (e.g. long polling)
• nginx with tcp module: in this case I think you need an additional port for this module (never tried this myself)
• put something else in front as a reverse proxy: I use HAProxy (which supports websockets) in front of nginx and node. Nginx now simply acts as a static fileserver, not a proxy. Varnish is another option, if you want additional caching.

Nginx – (13: Permission denied) while connecting to upstream:[nginx]

Make sure there are no security implications for your use-case before running this.

I had a similar issue getting Fedora 20, Nginx, Node.js, and Ghost (blog) to work. It turns out my issue was due to SELinux .

This should solve the problem:

I checked for errors in the SELinux logs:

And found that running the following commands fixed my issue:

Option #2 (untested, but probably more secure)

https://security.stackexchange.com/questions/152358/difference-between-selinux-booleans-httpd-can-network-relay-and-httpd-can-net

http://blog.frag-gustav.de/2013/07/21/nginx-selinux-me-mad/ https://wiki.gentoo.org/wiki/SELinux/Tutorials/Where_to_find_SELinux_permission_denial_details http://wiki.gentoo.org/wiki/SELinux/Tutorials/Managing_network_port_labels

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nginx - connect() failed upstream under load testing

I've been doing some load testing with wrk of my nginx reverse proxy -> my web app setup and I noticed that when I get to 1000+ concurrent connections, nginx starts returning 502s and the following error message:

the wrk command was:

I'm trying to figure out what might have gone wrong here. My web application is listening to requests proxied by nginx at port 3004. Is nginx running out of ports? Is the web application not able to handle this many request? Are requests being timed out? I'm not clear on this and would love to have more insight into it.

• reverse-proxy
• load-testing

• 1 Seems you've run out of local ports due to sockets in TIME-WAIT state. You can try using bigger local port range, set keepalive for connections, or using unix sockets to connect to backends. See serverfault.com/questions/649262/… –  Federico Sierra Apr 17, 2015 at 21:15
• Consider github.com/lebinh/ngxtop for additional insights. NgxTop shows many more metrics based on those logs. –  JayMcTee Apr 11, 2016 at 9:12

2 Answers 2

Already answered here: https://stackoverflow.com/questions/14144396/nginx-proxy-connect-to-ip80-failed-99-cannot-assign-requested-address

The message suggests you've run out of local sockets/ports.

Try to increase networking limits:

Alternatively you may try unix sockets to see if it helps.

Overview of Network Sockets When a connection is established over TCP, a socket is created on both the local and the remote host. The remote IP address and port belong to the server side of the connection, and must be determined by the client before it can even initiate the connection. In most cases, the client automatically chooses which local IP address to use for the connection, but sometimes it is chosen by the software establishing the connection. Finally, the local port is randomly selected from a defined range made available by the operating system.The port is associated with the client only for the duration of the connection, and so is referred to as ephemeral. When the connection is terminated, the ephemeral port is available to be reused.

Solution Enabling Keepalive Connections

Use the keepalive directive to enable keepalive connections from NGINX to upstream servers, defining the maximum number of idle keepalive connections to upstream servers that are preserved in the cache of each worker process. When this number is exceeded, the least recently used connections are closed. Without keepalives you are adding more overhead and being inefficient with both connections and ephemeral ports.

more : https://www.nginx.com/blog/overcoming-ephemeral-port-exhaustion-nginx-plus/

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Troubleshooting

Unable to connect: Can’t assign requested address

Last updated: January 11, 2023

Note:  This article is for users with technical experience. For other users, please  contact the ExpressVPN Support Team for direct assistance .

Users who recently changed to ExpressVPN may see an error message in their diagnostics similar to this:

MANAGEMENT: Socket bind failed on local address [AF_INET]180.168.41.175:49314: Can't assign requested address

If you see this message, the problem may be that your host file is missing some important lines. To confirm:

• Open  Terminal
• In Terminal, type “ ping localhost “
• You should see something like the below: 64 bytes from 127.0.0.1: icmp_seq=0 ttl=64 time=0.064 ms 64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.069 ms 64 bytes from 127.0.0.1: icmp_seq=2 ttl=64 time=0.303 ms
• To stop, hit  Control + C

If you see an IP address that is NOT 127.0.0.1, your host file is missing some important lines. To fix this:

• Open  Terminal  via Spotlight Search (command + space, then type “terminal”)
• In Terminal, enter  sudo nano /private/etc/hosts
• Enter your admin password. You will not be able to see which characters you input so type carefully.
• Your host file will be loaded onto Terminal. Use the arrow keys to navigate between lines in the file.
• Enter the below three lines if you do not see them in your host file: 127.0.0.1 localhost 255.255.255.255 broadcasthost ::1 localhost

• Press  Control + X to quit editing the host file
• You will need to flush the existing DNS cache for the entries to be effective. See instructions on flushing the DNS cache .
• Open ExpressVPN and connect to a server location

Need help? Contact the ExpressVPN Support Team via Live Chat for immediate assistance .

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Running ingress as transparent proxy getting "Cannot assign requested address" error

can someone help to solve this issue ?

bash-4.2# nginx -v nginx version: nginx/1.14.0 (1.14.0-1) bash-4.2# tailf /var/log/nginx/error.log 2018/06/20 02:49:22 [crit] 247#247: *4 bind(10.136.207.94:58900) failed (99: Cannot assign requested address) while connecting to upstream, udp client: 10.136.207.94, server: 0.0.0.0:53, upstream: “192.168.1.192:53”, bytes from/to client:39/0, bytes from/to upstream:0/0

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nginx proxy: connect() to ip:80 failed (99: Cannot assign requested address)

Answer a question An nginx/1.0.12 running as a proxy on Debian 6.0.1 starts throwing the following error after running for a short time: connect() to upstreamip:80 failed (99: Cannot assign requested

weixin_0010034

Answer a question.

An nginx/1.0.12 running as a proxy on Debian 6.0.1 starts throwing the following error after running for a short time:

Not all requests produce this error, so I suspect that it has to do with the load of the server and some kind of limit it hit.

I have tried raising ulimit -n to 50k and worker_rlimit_nofile to 50k as well, but that does not seem to help. lsof -n shows a total of 1200 lines for nginx. Is there a system limit on outgoing connections that might prevent nginx from opening more connections to its upstream server?

Seems like I just found the solution to my own question: Allocating more outgoing ports via

solved the problem.

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