Use static IP to enable DHCP service of router

This is a short manual to repair a home network environment in case the DHCP server is offline. There are some assumptions about the setup of the home network environment. It has been tested with a client using GNU Guix, MATE Desktop Environment and Network Manager.

Scenario

The DHCP service is separated from the router (different host).

The DHCP server is offline and cannot get online again.

A client cannot connect to the router to enable the DHCP service there because the client does not get an IP address.

Network Manager is installed on the client.

An Ethernet connection to the router is possible (LAN).

Goal

Login to the web admin page of the router by using a static IP address for the client.

Some example values

The router IP is 192.168.178.1.

The DHCP server would hand out IP addresses from 192.168.178.20 to 192.168.178.200.

Steps

Edit Network Manager connections.

Select the wired connection of the Ethernet network.

Edit IPv4 settings:

Set method to "Manual".

Add a new address with an IP which would not be handed out by your DHCP service (e.g. "192.168.178.254"), set the netmask (e.g. "24" for 192.168.178.0/24) and set the gateway to the IP of the router (e.g. "192.168.178.1").

Save settings.

Reset the Ethernet connection (e.g. via Network Manager or pull out the Ethernet cable and plug it in again).

Browse to the web admin page (e.g. https://192.168.178.1), login and enable the DHCP service of the router.

Reset IPv4 settings of the client and reset the Ethernet connection again.