On Wed, Dec 28, 2011 at 04:58:19AM +0530, Glen Kent wrote: > It seems ISIS and OSPFv3 use the link local next-hop in their route > advertisements. > > We discussed that SLAAC doesnt work with prefixes > 64 on the ethernet > medium (which i believe is quite, if not most, prevalent). If thats > the case then how are operators who assign netmasks > 64 use ISIS and > OSPF, since these protocols will use the link local address? > > I had assumed that nodes derive their link local address from the > Route Advertisements. They derive their least significant 64 bytes > from their MACs and the most significant 64 from the prefix announced > in the RAs.
Each prefix on an interface can have a different prefix length. Link-locals always have a prefix length of 64, even if a global address assigned to the same interface has a different length. Also, the link-local address is derived locally without any information from RAs.