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.