Category Archives: Networking

Setting MTU with netplan

It took me a bit to figure out how to set an interface MTU using the new netplan that ships with Ubuntu 18.04. Netplan works by taking a YAML file and generating systemd-networkd configuration scripts. I found another post that indicated the reason MTU settings wasn’t working had to do with the generated “Match” clause for the inteface name was against the original (pre-udev-renaming) name. The post indicated they switched to a macaddress match instead, this also worked for me:

network:
  version: 2
  renderer: networkd
  ethernets:
    # Configure MTU
    bigmtu1:
      match:
        macaddress: 00:e0:8d:7e:1f:37
      mtu: "9000"

yields:

00:00 [13:24:19 hyperion:~]$ more /run/systemd/network/10-netplan-bigmtu1.link
[Match]
MACAddress=00:e0:8d:7e:1f:37

[Link]
WakeOnLan=off
MTUBytes=9000