Home / ubuntu / Questions / 1332072
Accepted
WoJ
Asked: 2021-04-18 09:03:28 +0800 CST

How to assign the same static IP to a wired and wireless NIC?

  • 772

I have a machine (18.04, will be 20.04 at some point) that has a wired NIC as well as a USB card with a wireless one. It is usually connected by cable, but sometimes the cable is disconnected (mechanically, by someone, for various reasons).

I would like to ensure that the static IP 192.168.10.1 is always reachable:

  • either via the cable when it is plugged in,
  • or via Wi-Fi when it is not.

Is there a standard (or at least reasonable) way to do this?

I saw an answer to a question that was suggesting to assign this IP to the lo interface:

ip address add IP/32 dev lo

but I am not sure this is a reasonable approach?

networking

1 Answers

  1. Best Answer

    The solution was to use networkd-dispatcher. It can be installed via apt install networkd-dispatcher but it was already installed on my system.

    It creates /usr/lib/networkd-dispatcher and in there (among others)

    • no-carrier.d → this is where to put the script to turn wifi on
    • routable.d → this is where to put the script to turn wifi off

    I made two scripts along the lines of

    #!/bin/bash

# must be /bin/bash, for some reasons /bin/sh does not work
# br0 should be replaced by the interface that goes up and down when the cable is plugged in/out
# wlx1cbfce22a2cc to be replaced by the name of the wifi interface

if [ "$IFACE" == "br0" ]
then
    echo "disabling wifi because cable is in"
    /sbin/ifconfig wlx1cbfce22a2cc down
fi

    I fixed the IP of the wireless card to the same one as the wired one - only one of them is live at a given time.

    • 2