I cannot verify this is working on bionic with ipv6 static addresses. root@ubuntu:~# lsb_release -rd Description: Ubuntu 18.04.3 LTS Release: 18.04 root@ubuntu:~# cat /etc/cloud/build.info build_name: server serial: 20191021 root@ubuntu:~# uname -a Linux ubuntu 4.15.0-66-generic #75-Ubuntu SMP Tue Oct 1 05:24:09 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux root@ubuntu:~# apt-cache policy netplan.io netplan.io: Installed: 0.98-0ubuntu1~18.04.1 Candidate: 0.98-0ubuntu1~18.04.1 Version table: *** 0.98-0ubuntu1~18.04.1 500 500 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages 100 /var/lib/dpkg/status 0.40.1~18.04.4 500 500 http://security.ubuntu.com/ubuntu bionic-security/main amd64 Packages 0.36.1 500 500 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages root@ubuntu:~# apt-cache policy systemd systemd: Installed: 237-3ubuntu10.31 Candidate: 237-3ubuntu10.31 Version table: *** 237-3ubuntu10.31 500 500 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages 100 /var/lib/dpkg/status 237-3ubuntu10.29 500 500 http://security.ubuntu.com/ubuntu bionic-security/main amd64 Packages 237-3ubuntu10 500 500 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages root@ubuntu:~# cat /etc/netplan/50-cloud-init.yaml # This file is generated from information provided by # the datasource. Changes to it will not persist across an instance. # To disable cloud-init's network configuration capabilities, write a file # /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following: # network: {config: disabled} network: version: 2 ethernets: interface0: dhcp4: true match: macaddress: '52:54:00:12:34:00' set-name: interface0 interface1: dhcp4: false dhcp6: false addresses: - 192.168.1.2/24 - 2001:4800:78ff:1b:be76:4eff:fe06:1000/64 match: macaddress: '52:54:00:12:34:02' mtu: 6666 ipv6-mtu: 5634 set-name: interface1 accept-ra: false dhcp6-overrides: use-mtu: false link-local: [ ] root@ubuntu:~# ip link show interface1 3: interface1: mtu 6666 qdisc fq_codel state UP mode DEFAULT group default qlen 1000 link/ether 52:54:00:12:34:02 brd ff:ff:ff:ff:ff:ff # sysctl net.ipv6.conf.interface1.mtu net.ipv6.conf.interface1.mtu = 6666 root@ubuntu:~# cat /run/systemd/network/10-netplan-interface1.link [Match] MACAddress=52:54:00:12:34:02 [Link] Name=interface1 WakeOnLan=off MTUBytes=6666 root@ubuntu:~# cat /run/systemd/network/10-netplan-interface1.network [Match] MACAddress=52:54:00:12:34:02 Name=interface1 [Network] LinkLocalAddressing=no Address=192.168.1.2/24 Address=2001:4800:78ff:1b:be76:4eff:fe06:1000/64 IPv6AcceptRA=no IPv6MTUBytes=5634 # journalctl -o short-precise -b 0 | egrep -i "(MTU|interface1)" Oct 23 21:28:47.968910 ubuntu kernel: virtio_net virtio3 interface1: renamed from ens6 Oct 23 21:28:50.636014 ubuntu systemd-networkd[670]: Ignoring /run/systemd/network/10-netplan-interface1.network, because it's not a regular file with suffix .netdev. Oct 23 21:28:50.636090 ubuntu systemd-networkd[670]: Ignoring /run/systemd/network/10-netplan-interface1.link, because it's not a regular file with suffix .netdev. Oct 23 21:28:50.636706 ubuntu systemd-networkd[670]: Ignoring /run/systemd/network/10-netplan-interface1.link, because it's not a regular file with suffix .network. Oct 23 21:28:50.640507 ubuntu systemd-networkd[670]: interface7: Saved original MTU: 1500 Oct 23 21:28:50.642454 ubuntu systemd-networkd[670]: interface6: Saved original MTU: 1500 Oct 23 21:28:50.643050 ubuntu systemd-networkd[670]: interface5: Saved original MTU: 1500 Oct 23 21:28:50.643629 ubuntu systemd-networkd[670]: interface4: Saved original MTU: 1500 Oct 23 21:28:50.644214 ubuntu systemd-networkd[670]: interface3: Saved original MTU: 1500 Oct 23 21:28:50.644939 ubuntu systemd-networkd[670]: interface2: Saved original MTU: 1500 Oct 23 21:28:50.645025 ubuntu systemd-networkd[670]: interface1: New device has no master, continuing without Oct 23 21:28:50.645107 ubuntu systemd-networkd[670]: interface1: Flags change: +MULTICAST +BROADCAST Oct 23 21:28:50.645175 ubuntu systemd-networkd[670]: interface1: Link 3 added Oct 23 21:28:50.645456 ubuntu systemd-networkd[670]: interface1: udev initialized link Oct 23 21:28:50.647448 ubuntu systemd-networkd[670]: interface1: Saved original MTU: 6666 Oct 23 21:28:50.648100 ubuntu systemd-networkd[670]: interface0: Saved original MTU: 1500 Oct 23 21:28:50.648670 ubuntu systemd-networkd[670]: lo: Saved original MTU: 0 Oct 23 21:28:50.655303 ubuntu systemd-networkd[670]: interface1: Interface name change detected, interface1 has been renamed to ens6. Oct 23 21:28:50.655431 ubuntu systemd-networkd[670]: ens6: Interface name change detected, ens6 has been renamed to interface1. Oct 23 21:28:50.675541 ubuntu systemd-networkd[670]: interface1: Link state is up-to-date Oct 23 21:28:50.675782 ubuntu systemd-networkd[670]: interface1: found matching network '/run/systemd/network/10-netplan-interface1.network' Oct 23 21:28:50.677101 ubuntu systemd-networkd[670]: interface1: Bringing link up Oct 23 21:28:50.677242 ubuntu systemd-networkd[670]: interface1: IPv6 successfully enabled Oct 23 21:28:50.683588 ubuntu systemd-networkd[670]: interface1: Link does not request DHCPv6 prefix delegation Oct 23 21:28:50.686958 ubuntu systemd-networkd[670]: interface1: Flags change: +UP +LOWER_UP +RUNNING Oct 23 21:28:50.687472 ubuntu systemd-networkd[670]: interface1: Started LLDP. Oct 23 21:28:50.687554 ubuntu systemd-networkd[670]: interface1: Gained carrier Oct 23 21:28:50.687842 ubuntu systemd-networkd[670]: interface1: Setting addresses Oct 23 21:28:50.697061 ubuntu systemd-networkd[670]: interface1: Updating address: 192.168.1.2/24 (valid forever) Oct 23 21:28:50.698167 ubuntu systemd-networkd[670]: interface1: Addresses set Oct 23 21:28:52.021563 ubuntu systemd-networkd[670]: interface1: Adding address: fe80::5054:ff:fe12:3402/64 (valid forever) Oct 23 21:28:52.021588 ubuntu systemd-networkd[670]: interface1: Gained IPv6LL Oct 23 21:28:52.053025 ubuntu systemd-networkd[670]: interface1: Updating address: 2001:4800:78ff:1b:be76:4eff:fe06:1000/64 (valid forever) Oct 23 21:28:52.053125 ubuntu systemd-networkd[670]: interface1: Configured Oct 23 21:28:52.056906 ubuntu systemd-networkd-wait-online[691]: managing: interface1 Oct 23 21:28:52.216772 ubuntu systemd-networkd-wait-online[691]: managing: interface1