[rbridge] I got some answers from the IS-IS mailing list
Radia.Perlman at sun.com
Sat Jun 16 19:35:07 PDT 2007
Oh definitely. We need both (putting 0 into the area address, and either
address or a bit in the header).
Dinesh G Dutt wrote:
> Hi Radia,
> Radia Perlman wrote:
>> 1) They have deployed a variant of IS-IS, and the way they
>> distinguish their instances
>> is based on having a new multicast address. I wrongly remembered
>> IS-IS, and thought that
>> PSNPs got unicast, but even those are multicast (and I remember the
>> reasoning at the
>> time this was decided 100 years ago, which was to suppress lots of
>> routers sending the
>> same PSNP). So, for encoding TRILL IS-IS, it can be differentiated
>> from layer 3 IS-IS
>> by having a different multicast address. The bit in the header works
>> too, however.
>> 2) I checked to make sure that "0" would be OK to use as an area
>> address, and it is.
> My reading of what they recommended is that we use a different
> multicast address since it was not guaranteed that all implementations
> would support a 0 in the area address.
> Here is a pointer to the email from Mike Shand:
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