Add default route on physical interface using `systemd-networkd`

Question

In /lib/systemd/network/10-eth0.network on my client, I am failing to configure anything that can translate my manual command:

sudo ip route add default via 192.168.7.1 dev eth0 

where 192.168.7.1 is the static IPv4 address of my host.

My last 10-eth0.network configuration attempt:

[Match] Name=eth0 [Link] RequiredForOnline=no [Route] Address=192.168.7.2/24 Destination=192.168.7.1/32 Gateway=192.168.7.1 

Refreshed with sudo systemctl restart systemd-networkd and validated with ip route (it doesn't show up).

See also:

• [Route] Section Options
• Answers that aren't working: systemd-networkd and direct routes

Answer 1

You didn't specify anywhere that it's supposed to be the default route; instead you have Destination=192.168.7.1/32 – which is the complete opposite of a default route... as well as being a cyclical (self-referencing) route. According to your configuration, it probably shows up as a 192.168.7.1/32 dev eth0 in your route output (that would be the effective interpretation assuming the kernel doesn't reject it).

The default route is always 0.0.0.0/0, i.e. a lowest-precedence catch-all route, and that's what you need to define as the Destination=. (Alternatively you can omit Destination= entirely.)

A route via Gateway=192.168.7.1 can only be defined if you are in the same subnet. For that, make sure that the Address=192.168.7.2 parameter is either in an [Address] section or in the [Network] section – it makes no sense in the [Route] section.