netplan default gateway / route Internet traffic to WiFi

Question

I need help with a (simple) network configuration with netplan. It is very simple, I have 2 NICs: enp5s0 is ethernet and give access to the company network, and wlp4s0 is WiFi and give access to Internet via a router.

I just want the Internet traffic to be routed via the WiFi connection. The netplan configuration should be something like:

network:
  version: 2
  renderer: NetworkManager
  ethernets:
    enp5s0:
      dhcp4: true
      routes:
        - to: 192.168.1.0/24
          via: 192.168.1.1
  wifis:
    wlp4s0:
      dhcp4: true
      access-points:
        "My WiFi Network":
          password: "foobar"
      gateway4: 10.128.128.128
      routes:
        - to: 0.0.0.0/0
          via: 10.128.128.128

But it is not working. Surprisingly it is very easy to add the routes from the command line:

sudo route add -net 192.168.1.0 netmask 255.255.255.0 gw 192.168.1.1 dev enp5s0
sudo route del default gw 192.168.1.1
sudo route add default gw 10.128.128.128

And this works like a charm. I just want to do that with netplan...

You can't use `gateway4` and `routes` at the same time. Comment out `gateway4`. — heynnema, Jun 20 '19 at 14:55

score 0 · Answer 1 · answered Jun 07 '19 at 17:48

I answer to myself: dhcp may reset the default gateway, and the metrics we could specify in the netplan configuration are also overridden.

This works:

network:
  version: 2
  renderer: NetworkManager
  ethernets:
    enp5s0:
      dhcp4: false
      addresses: [192.168.1.143/24]
      routes:
        - to: 192.168.1.0/24
          via: 192.168.1.1
          metric: 10
  wifis:
    wlp4s0:
      dhcp4: true
      access-points:
        "My WiFi Network":
          password: "foobar"
      gateway4: 10.128.128.128

Was my answer helpful? You could change `dhcp4: true`, add the `use-routes: false`, and remove the static address. — heynnema, Jun 14 '19 at 00:00

score 0 · Answer 2 · edited Jun 12 '20 at 14:37

This information should help.

DHCP Overrides

Several DHCP behavior overrides are available. Most currently only have any effect when using the networkd backend, with the exception of use-routes and route-metric.

Overrides only have an effect if the corresponding dhcp4 or dhcp6 is set to true.

If both dhcp4 and dhcp6 are true, the networkd backend requires that dhcp4-overrides and dhcp6-overrides contain the same keys and values. If the values do not match, an error will be shown and the network configuration will not be applied.

use-routes (bool)

Default: true. When true, the routes received from the DHCP server will be installed in the routing table normally. When set to false, routes from the DHCP server will be ignored: in this case, the user is responsible for adding static routes if necessary for correct network operation. This allows users to avoid installing a default gateway for interfaces configured via DHCP. Available for both the networkd and NetworkManager backends.

And read the section:

Routing

source: https://netplan.io/reference

netplan default gateway / route Internet traffic to WiFi

2 Answers2

DHCP Overrides

Routing

Linked