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Tomas.R
Asked: 2020-08-15 04:57:09 +0800 CST

Modifying default gateway with nmcli (Ubuntu 18.04 LTS)

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I want to change my default gateway just to see how nmcli command works. So this is what I do.

I find out what my default gateway is :

ip route

default via 192.168.1.254 dev wlp9s0 proto dhcp metric 600 
169.254.0.0/16 dev wlp9s0 scope link metric 1000 
192.168.1.0/24 dev wlp9s0 proto kernel scope link src 192.168.1.216 metric 600 
192.168.122.0/24 dev virbr0 proto kernel scope link src 192.168.122.1 linkdown

I then bring my connection down

nmcli con down Telia-2F1C

Afterwards I try to change a default gateway but I get an error message, why ?

nmcli con mod Telia-2F1C ipv4.gateway 192.168.1.222
Error: Failed to modify connection 'Telia-2F1C': ipv4.gateway: gateway cannot be set if there are no addresses configured

or I add a subnet mask to a command and I get a different error message, but still nothing works

nmcli con mod Telia-2F1C ipv4.gateway 192.168.1.222/24

Error: failed to modify ipv4.gateway: invalid gateway address '192.168.1.222/24'.

How do I change the default gateway ?

networking

1 Answers

  1. You are adding a subnet mask at the end of the gateway IP address. You only use subnet mask '/24' to determine the size of a network with your IP address. For example, if you want to change your IP address on a you would write:

    nmcli connection modify Telia-2F1C ipv4.addresses 192.168.1.222/24

    Note the '/24' at the end of the address which tells the computer how many IP addresses are in that network.

    If you want to change the gateway you would write:

    nmcli con mod Telia-2F1C ipv4.gateway 192.168.1.1

    Note that there is no need to add the subnet at the end.

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