subnet prefix length > 64 breaks IPv6?

Glen Kent glen.kent at
Tue Dec 27 23:28:19 UTC 2011

It seems ISIS and OSPFv3 use the link local next-hop in their route

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.


On Tue, Dec 27, 2011 at 6:25 AM, Glen Kent <glen.kent at> wrote:
> Sven,
>> also various bgp implementations will send the autoconfigure crap ip as the
>> next-hop instead of the session ip, resulting in all kinds of crap in your
>> route table (if not fixed with nasty hacks on your end ;) which doesn't
>> exactly make it easy to figure out which one belongs to which peer
>> all the more reason not to use that autoconfigure crap ;)
> As per RFC 2545 BGP announces a global address as the next-hop. Its
> only in one particular case that it advertises both global and link
> local addresses.
> So, i guess, BGP is not broken.
> Its only RIPng afaik that mandates using a link local address.
> Glen

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