subnet prefix length > 64 breaks IPv6?

Glen Kent glen.kent at gmail.com
Tue Dec 27 17:28:19 CST 2011


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.

Glen

On Tue, Dec 27, 2011 at 6:25 AM, Glen Kent <glen.kent at gmail.com> 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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