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I am using systemd-networkd. I have one NIC and I am using the following configuration to create multiple IPs:

[Match]
Name=usbceth0

[Network]
DHCP=ipv4
DNS=8.8.8.8
DNS=8.8.4.4

# LAN_1
[Address]
Label=usbceth0:0
Address=192.168.100.10/24

# LAN_2 (4G-LAN)
[Address]
Label=usbceth0:1
Address=192.168.50.70/24

If there is a DHCP, usbceth0 gets an IP and gets a gateway assigned. The two added IPs, usbceth0:0 and usbceth0:1 are created normally. I need those to access different LANs. So far so good.

The network of usbceth0:1 has also a gateway at 192.168.50.1.

How can I add this gateway as-well in my configuration? Configure two gateways, one coming from the DHCP and one the 192.168.50.1. Is it possible?

Thanks!

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1 Answer 1

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If I understand correctly your primary route (gateway) would be the one from the DHCP and the second would be a back up. So, you can set a static route with bigger metric, which comes in only if the primary is down. You can check your current metrics with route -n.

Using the systemd-networkd the .network file should look like:

[Match]
Name=usbceth0

[Network]
DHCP=ipv4
DNS=8.8.8.8
DNS=8.8.4.4

# LAN_1
[Address]
Label=usbceth0:0
Address=192.168.100.10/24

# LAN_2 (4G-LAN)
[Address]
Label=usbceth0:1
Address=192.168.50.70/24

# "Static"-Gateway as backup
[Route]
Gateway=192.168.50.1
#Destination=0.0.0.0/0
Metric=1025 # The Gateway of the DHCP gets the default 1024

If it complains you can add Destination= and also you can use RouteMetric for the DHCP route if you want to make a custom metric. Don't forget to restart the systemd-networkd.service.

Or you can do it with ip route add 'Destination' via 'Gateway' metric but this won't stay after a reboot

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  • Correct Angel! The high level idea is this. But how do I configure this (literally)? Can this be done with systemd-networkd or iptables or some other way?
    – Tanasis
    May 2, 2020 at 8:23
  • I have edited my answer with the example but as I said above it is not tested so be careful
    – Angel
    May 2, 2020 at 11:02

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