Configuring computer names within a LAN

How to publish a computer name to Multicast DNS

I recently bought a Raspberry Pi and I wanted to be able to SSH into it. The problem is - what's its IP address?

Solution 1 - ifconfig

If I have a monitor/keyboard attached to the Pi, then I can run ifconfig and it produces output like:

wlan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.7.207  netmask 255.255.252.0  broadcast 192.168.7.255
        inet6 fe80::da3a:ddff:fe45:863f  prefixlen 64  scopeid 0x20<link>
        ether d8:3a:dd:45:86:3f  txqueuelen 1000  (Ethernet)
        RX packets 78677  bytes 46740811 (44.5 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 10826  bytes 1248499 (1.1 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

That means I can SSH into 192.168.7.207. This works, but it has a huge drawback: the IP address can change, so I need to attach a monitor/keyboard. This kind of obviates the need for SSH. It also produces SSH warning messages each time the IP address changes.

Solution 2 - pinning the IP address in my router

I use a EERO router, which has software which allows me to pin specific devices to specific IP addresses. So I can pin my PI to 192.168.7.207. I don't like to remember a sequence of numbers, so I add an entry to my /etc/hosts:

192.168.7.207 raspberry-pi

Now I can disconnect my monitor/keyboard and ssh raspberry-pi. But there are still some drawbacks:

  1. I need to configure the pinned IP address in some proprietary router software. If I change my router, I'll need to redo this work.

  2. I need to configure /etc/hosts on any device I use to ssh to raspberry-pi. If I ever need to change these addresses, it'll be a pain to track them all down.

Solution 3 - multicast DNS

This is my current solution, and I'm quite happy with it. I can configure my raspberry-pi to publish its name via Multicast DNS (aka mDNS). The software to do this for Linux is Avahi. On NixOS this can be setup as follows:

{
  networking.hostName = "raspberry-pi";

  # Enable LAN hostname resolution (so other machines on the same LAN can find
  # this one)
  services.avahi = {
      enable = true;
      nssmdns = true;
      publish = {
        enable = true;
        addresses = true;
        domain = true;
        hinfo = true;
        userServices = true;
        workstation = true;
      };
  };
}

With mDNS I can ssh into my Pi with ssh raspberry-pi.local. Any machine on the same LAN can resolve this address. I don't need any external configuration.


If you enjoyed this post, please let me know on Twitter or Bluesky.

Posted December 29, 2023.

Tags: #linux

Index RSS About