Hi Users of BIRD!
I have only heard about "OSPF Unnumbered" a couple of times, and never
have seen any clear explanation or specific details. And based on that,
I had the false assumption that "unnumbered" would imply "having no
address on the interfaces"; maybe only an IPv4 address used as a
router-id as an `/32' assignment on loopback.
But without an address on an interface I have not seen any packets sent
to 224.0.0.5.
So I just gave it a try and added the `/32` from loopback on each
interface, too, and from the BIRD documentation I concluded I must set
`type ptp;` in the ospf area interface stanza... and.... Bingo.
It just works.
Later I discovered, that's the way how Cumulus recommends it with FRR.
[1] But couldn't have anyone told me this earlier? Next time maybe :)
So basically my question is: Is this the correct way as it is intended?
Is OSPFv2 unnumbered --how ever-- properly specified, or just a clever
way, which just happens to work? And: Is this compatible with NOS from
various vendors?
(As IPv6 offers link-local addresses, there is no need for OSPFv3
unnumbered, right?)
Are there any issues with that approach I'm unaware of?
Thanks for your time, and
have a nice Friday evening and weekend.
Bernd
PS: I tried this on Debian 11 with kernel 5.10 and bird 2.0.9
[1]
https://docs.nvidia.com/networking-ethernet-software/cumulus-linux-50/Layer-3/OSPF/Open-Shortest-Path-First-v2-OSPFv2/#ospfv2-unnumbered
