[bird-users] [bird-users] Re: Bird 2.x / OSPF v3 over ptp tunnels

[Chriztoffer Hansen]

Joakim Tjernlund wrote on 11/02/2020 19:27:
> On Tue, 2020-02-11 at 18:18 +0100, Alarig Le Lay wrote:
>> On mar. 11 févr. 17:52:29 2020, Bastien Durel wrote:
>>> 7: wg4b: <POINTOPOINT,NOARP,UP,LOWER_UP> mtu 1420 state UNKNOWN qlen 1000
>>>     inet6 fe80::3/128 scope link
>>>        valid_lft forever preferred_lft forever
>>> 8: wg4a: <POINTOPOINT,NOARP,UP,LOWER_UP> mtu 1420 state UNKNOWN qlen 1000
>>>     inet6 fe80::3/128 scope link
>>>        valid_lft forever preferred_lft forever
>>
>> Don’t put fe80 addresses by hand and definitely not with /128, let your
>> kernel handles this.
> 
> I always wondered why not /128 ? In IPV4 they are just fine.

Because IPv6 Link-Local *IS* using a /64 prefix. [0]
\-> rfc4291, Sec. 2.5.6 [1]

If you assign link local addresses with any other mask length than 64.
You cannot assume the software will behave as you expect. Because using
< 64 > is outside the scope of how the link local addresses are defined
in the RFC.

Chriztoffer

[0]: https://packetlife.net/blog/2011/apr/28/ipv6-link-local-addresses/
[1]: https://tools.ietf.org/html/rfc4291#section-2.5.6