Newbie IPv6 question

notty

Probably a very simple one. Two of my machines (both OVZ if it matters) have this address listed alongside the public IPv6 address:

inet6 ::2/128 scope global

I know ::1 is loopback but what is ::2 for and do I need it?

dedicados

is like gateway and your first ip

notty

Thanks, do you mean ::2 is a special address used just for the gateway? Is this an OpenVZ thing?

I read in various places that ::/96 is reserved for IPv4-compatible addresses (deprecated) so at first I thought it was something like that.

WSS

::2 is your first usable IP. CIDR networking is still a thing in IPv6.

:: just means <all unfilled up to your final not-an-octet. It's like shorthand for 127.0.0.1 in ipv4 being "127::1."

notty

Thanks. I think I do understand the notation. But I'm still confused, as ::2 surely isn't a public IP.
And yet it appears with "global" scope alongside my public IPs...

root@notty:~# ip -6 a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 state UNKNOWN qlen 1000
    inet6 ::1/128 scope host  <-- this is loopback
       valid_lft forever preferred_lft forever
2: venet0: <BROADCAST,POINTOPOINT,NOARP,UP,LOWER_UP> mtu 1500 state UNKNOWN
    inet6 abcd:ab:c:d::567b/64 scope global <-- these are my public IPs
       valid_lft forever preferred_lft forever
    inet6 ::2/128 scope global  <-- but what's this address??
       valid_lft forever preferred_lft forever

abnoeh

I think thats point to point link to upstream gateway?

Rahul

I was good at math until they mixed the alphabet into it.

lebuser

The IPv6 address ::2/128 used on Openvz 7 is invalid. Using it is completely broken. Bird also fills the log with:

KIF: Invalid interface address ::2 for venet0