Comment 11 for bug 1799487

Verification done for cosmic:

ubuntu@test-netplan-cosmic:~$ cat /etc/netplan/50-cloud-init.yaml | grep -A 10 'tunnels'
    tunnels:
        he-ipv6:
            mode: sit
            remote: xxx.xxx.xxx.xxx
            local: xxx.xxx.xxx.xxx
            addresses:
            - "2001:xxx:xx:xxx::2/64"
            gateway6: "2001:xxx:xx:xxx::1"
ubuntu@test-netplan-cosmic:~$ ip -6 addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 state UNKNOWN qlen 1000
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: ens3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 state UP qlen 1000
    inet6 fe80::f816:3eff:fed1:a358/64 scope link
       valid_lft forever preferred_lft forever
4: he-ipv6@NONE: <POINTOPOINT,NOARP,UP,LOWER_UP> mtu 1480 state UNKNOWN qlen 1000
    inet6 2001:xxx:xx:xxx::2/64 scope global
       valid_lft forever preferred_lft forever
    inet6 fe80::3627:b7f0/64 scope link
       valid_lft forever preferred_lft forever
ubuntu@test-netplan-cosmic:~$ ping6 2620:119:35::35
PING 2620:119:35::35(2620:119:35::35) 56 data bytes
64 bytes from 2620:119:35::35: icmp_seq=1 ttl=61 time=19.5 ms
64 bytes from 2620:119:35::35: icmp_seq=2 ttl=61 time=17.4 ms
64 bytes from 2620:119:35::35: icmp_seq=3 ttl=61 time=17.1 ms
64 bytes from 2620:119:35::35: icmp_seq=4 ttl=61 time=17.3 ms
^C
--- 2620:119:35::35 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 8ms
rtt min/avg/max/mdev = 17.129/17.821/19.477/0.964 ms
ubuntu@test-netplan-cosmic:~$ dpkg -l netplan.io | grep ii
ii netplan.io 0.96-0ubuntu0.18.10.2 amd64 YAML network configuration abstraction for various backends
ubuntu@test-netplan-cosmic:~$