I've added "mtu: 9000" to the bonds section, which now reads as follows;
bonds: eth1: mtu: 9000 interfaces: - enp5s0f0 - enp5s0f1 - enp6s0f0 - enp6s0f1 parameters: down-delay: 0 lacp-rate: fast mii-monitor-interval: 100 mode: 802.3ad transmit-hash-policy: encap3+4 up-delay: 0 I re-ran netplan apply, but the bond had the same MTU as before. I also tried restarting systemd-networkd as I could see that the relevant .netdev files in /run/systemd/network/ had MTUBytes set to 9000. However, the interface remained at 1500 bytes. After a system restart however, the bond interface is now running at a MTU of 9000. dmesg now only has messages for the member interfaces being increased from 1500 to 9000 MTU - the messages regarding the MTU being lowered from 9000 to 1500 when the bond was being configured are no longer present. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1774666 Title: Bond interfaces stuck at 1500 MTU on Bionic To manage notifications about this bug go to: https://bugs.launchpad.net/cloud-init/+bug/1774666/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs