5

I'm trying to configure static IPv6 with netplan on a cloud server (public cloud from OVH) running Ubuntu 18.04

I have created a /etc/netplan/66-ipv6.yaml yaml file in addition to the existing /etc/netplan/50-cloud-init.yaml :

network:
    version: 2
    ethernets:
        ens3:
            match:
              name: ens3
            addresses: 
              - '2001:what:ever::1234/128'
            gateway6: '2001:what:ever::1'

Wether manually with netplan generate; netplan apply or on reboot, the interface get its static IPv6 address but gateway6: seems to have no effect at all.

me@server:~$ ip -6 route
2001:what:ever::1234 dev ens3 proto kernel metric 256 pref medium
fe80::/64 dev ens3 proto kernel metric 256 pref medium

Obviously the server can't reach any public IPv6 address at this point.

me@server:~$ ping6 google.com
connect: Network is unreachable

Manually adding the default route works fine.

me@server:~$ sudo ip -6 route add 2001:what:ever::1 dev ens3
me@server:~$ sudo ip -6 route add default via 2001:what:ever::1 dev ens3
me@server:~$ ip -6 route
2001:what:ever::1 dev ens3 metric 1024 pref medium
2001:what:ever:1234 dev ens3 proto kernel metric 256 pref medium
fe80::/64 dev ens3 proto kernel metric 256 pref medium
default via 2001:what:ever::1 dev ens3 metric 1024 pref medium
me@server:~$ ping6 -c 1 google.com
PING google.com(par10s27-in-x0e.1e100.net (2a00:1450:4007:809::200e)) 56 data bytes
64 bytes from par10s27-in-x0e.1e100.net (2a00:1450:4007:809::200e): icmp_seq=1 ttl=53 time=7.54 ms

--- google.com ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 7.544/7.544/7.544/0.000 ms

Am I missing something very obvious ?

8

Subnets are (almost) always a /64. You configured your interface as a /128, which is only a single address. That means the gateway is on a different subnet and can't be reached.

What you probably want is to configure the address as a /64, and everything should work. The /64 is just a subnet mask. You're still assigning only a single address.

  • This is indeed the correct answer, I can't believe how obvious that was. Thanks @SanderSteffann – duch Jun 14 '18 at 19:38

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