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-...