Router ID on IPv6-Only

Saku Ytti saku at
Thu Sep 8 05:50:18 UTC 2022


> Well, now there is no IPv4. But BGP, OSPFv3, and other routing protocols still use 32-bit router IDs for IPv6. On the one hand, there are plenty of 32-bit numbers to use. Generally speaking, router IDs just need to be unique inside of an AS to do their job, but (a) for humans or automation to generate them and (b) to easily recognize them, it's convenient to have some algorithm or methodology for assigning them.

2nd hand knowledge, but when this was discussed early on in
standardization, someone argued against 128b ID, because it would
require too much bandwidth in their OSPF network. Joys of everyone
plays standardisation.

> Has anyone thought about this or have a good way to do it? We had ideas like use bits 32-63 from an interface. Seems like it could work, but also could totally break down if we're using >64-bit prefixes for things like router-to-router links or pulling router loopbacks out of a common /64.

If your data is in a database I think the best bet is to
algorithmically generate multiple forms of IDs in your device and
interface rows, to satisfy various restrictions on what forms  of IDs
are accepted. And then use these IDs. If your data is in configs, you
don't have really good solutions, but you could choose 32b from your
IPv6 loopback right side :/.


More information about the NANOG mailing list