I'm having a similar issue where setting the MTU to 1500 and using a match on mac address does not stick. This is on a EC2 T2.Medium instance. Actual configuration from a dev server: network: version: 2 ethernets: eth0: match: macaddress: 12:0f:ae:49:5d:06 mtu: 1500 dhcp4: true nameservers: search: [ devbuilds.vpc, ec2.internal ]
$> cat /var/run/systemd/network/10-netplan-eth0.link [Match] MACAddress=12:0f:ae:49:5d:06 [Link] WakeOnLan=off MTUBytes=1500 $> cat /var/run/systemd/network/10-netplan-eth0.network [Match] MACAddress=12:0f:ae:49:5d:06 [Network] DHCP=ipv4 Domains=devbuilds.vpc ec2.internal [DHCP] UseMTU=true RouteMetric=100 $> ip link show eth0 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9001 qdisc mq state UP mode DEFAULT group default qlen 1000 link/ether 12:0f:ae:49:5d:06 brd ff:ff:ff:ff:ff:ff # manually set MTU $> sudo ip link set dev eth0 mtu 1500 $> ip link show eth0 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000 link/ether 12:0f:ae:49:5d:06 brd ff:ff:ff:ff:ff:ff $> sudo netplan generate $> sudo netplan apply $> ip link show eth0 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9001 qdisc mq state UP mode DEFAULT group default qlen 1000 link/ether 12:0f:ae:49:5d:06 brd ff:ff:ff:ff:ff:ff The last netplan commands could be replaced with a reboot with the same result. This configuration seemed to help others, so hopefully i'm simply missing something or perhaps this is related to EC2? Attaching output of cloud-init ** Attachment added: "Result of cloud-init collect-logs" https://bugs.launchpad.net/netplan/+bug/1724895/+attachment/5219532/+files/cloud-init-logs-2018-12-05.tgz -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1724895 Title: MTU not applied on private ethernet interfaces To manage notifications about this bug go to: https://bugs.launchpad.net/cloud-init/+bug/1724895/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs