On Mon, Apr 01, 2024 at 04:14:51PM +0200, Sebastian Hahn wrote: > > Sebastian - my interpretation of 5838 is slightly different, and I don't > > think it expressly forbids xAF nexthops: > > > 2.5: Although IPv6 link local addresses could be used as next hops for > > > IPv4 address families, it is desirable to have IPv4 next-hop addresses. > > My understanding came from this: > > > In order to achieve this, the link's IPv4 address will be advertised > > in the "link local address" field of the IPv4 instance's Link-LSA. > > This address is placed in the first 32 bits of the "link local > > address" field and is used for IPv4 next-hop calculations. The > > remaining bits MUST be set to zero. > > which to me reads like the statement about desirability just explains > why the technical design doesn't allow IPv6 next hops. I would be > happy to be wrong here.
Hi Unfortunately, RFC 5838 chose the worst way to represent IPv4 in Link-LSA, so there is no reliable way to know whether received Link-LSA should be interpreted as IPv4 or IPv6. Although one could have option that forces it to interpret as IPv6, i would prefer to have 'extended next hop' option that allows to accept both IPv4 and IPv6 next hops in Link-LSA. We could use heuristic, like if first u32 is fe800000, it is IPv6, if remaining u32s are 0, it is IPv4, And hope that nobody uses both fe80::0 and 254.128.0.0. -- Elen sila lumenn' omentielvo Ondrej 'Santiago' Zajicek (email: santi...@crfreenet.org) "To err is human -- to blame it on a computer is even more so."
