[rbridge] Ingress Rbridge address and BCN - 3rd Issue

[Gray, Eric]

-- [SNIP] --     
 
--> > 3rd Issue - why use tunneling if RBridges typically may be required
--> > to retain all MAC reachability information?
--> > ========================================== 
--> > 
--> > 	There are several reasons to do this, independent of any desire to
--> > reduce memory requirements of RBridges. 
--> > 
--> > 	One is that 802.1X bridges on intermediate links are shielded from
--> > exposure to MAC addresses on separate bridged LAN segements. 
--> 
--> I thought that was accomplished by adding the additional MAC header
--> between the two RBridges carrying their MACs.  The 802.1X bridges
--> connecting them will only learn these two RBridges MACs regardless of
--> whether there is a destination RBridge in the shim.

Look, again, at the definition of the "3rd Issue" above.

>From you comment, it seems you missed that...

--> > 
--> > 	Another is that the forwarding entries in RBridges are based on use
--> > of RBridge MAC addresses - which reduces the number of entries that
--> > will typically be used for forwarding by an intermediate RBridge.  
--> 
--> I'm missing the destinction between what you call the "memory
requirements 
--> RBridges", and "the number of entries that will typeically be used for 
--> forwarding".  I was assuming these were the same thing.

They are separable in a number of different ways.  Trying to state it
at a high level, it is certainly possible to optimize your look-up 
algorithms for a subset of frequently used entries.  Caching comes to
mind, for example.

-->