[rbridge] Ingress Rbridge address and BCN - 2nd Issue

[Caitlin Bestler]

Larry Kreeger, responding to Eric Gray, wrote:
>> 
>> 1) Flooding will only occur when a specific RBridge has removed (due
>> to aging, for example), or failed to retain, an entry it
>> subsequently needs. This kind of flooding could occur in any case
>> (although it might involve a smaller subset of the entire network).
> 
> I understand that this will occur when an edge RBridge does
> not have an entry, but I assume that this will be a fairly
> rare condition.  Also, I am expecting the number of flows
> through an edge RBridge to be much less than throught a core
> RBridge, such that the number of MAC addresses entries needed
> would be much less at an edge RBridge.  If a core RBridge did
> not have a larger table, then it could get easily filled
> which would require flooding of the BCNs much more than would
> occur naturally at an edge RBridge.
> 
More fundamentally, the egress rbridge will in most case also
encapsulate the reverse-bound frames, and so will have had a 
reason to note the mac->rbridge mapping in the first place.
A "core rbridge" would not have forgotten the mapping, it would
have never looked for it in the first place. Table size is irrelevant.