Is this related to T20 ?

seems so but:

Linux kernel allowed this cause there are many valid setups for it (network namespaces, vrf, unnumbered interface and so on). So for me this is a bug not a feature.
It is not fixed. doing it manual it works like a charme.

As i see it this is a fundamental change and should not be allowed into 1.2 LTS but it migth be added to 1.3 (just a opinion, not a decition)

+1 on having this in 1.3 and not 1.2

In T1309#34455, @runar wrote:

As i see it this is a fundamental change and should not be allowed into 1.2 LTS but it migth be added to 1.3 (just a opinion, not a decition)

I don't see here an fundamental change. It is one line code change see pull request.
I't don't change any configuration, it don't break any configuration, no syntax change.

Lets test it first :)

@dmbaturin can you explain why we schedule it to the next release and not to 1.2.1 for example? Are there any policies?

From my point of view:

1. It don't break any older setups
2. No syntax change
3. But allow to use existing features

As far as I can see it is included in 1.2.1 so we can close this or?
If yes I will submit a config example for ospf ip unnumbered that uses it

Its only in the current branch for rolling, not in 1.2.1 crux - but can be backported

I have added the Documentation:

https://github.com/vyos/vyos-documentation/pull/58