[c-nsp] Layer 2 vs Layer 3 Performance Question

[Phil Mayers]

Kevin Graham wrote:
> 
> 
>> Hmm. I'm more familiar with the sup720/PFC3 hardware than the earlier stuff.
> 
> Sup2/MSFC2 is same switching paths as 720, only major difference is the common
> lack of a switch fabric.
> 
>> What IOS version are you running? Can you "show mod"?
>>
>> Are the servers & backup kit on the same linecard? If the linecard lacks a DFC, 
>> then it's possible having them on the same VLAN would buy you local layer2 
>> switching, versus a (potentially contended) layer3 lookup on the PFC/sup.
> 
> What local lookup are you expecting to occur on a non-DFC linecard? Unless I'm
> missing something, you're looking at the exact same switching path for L2 or
> L3. In terms of forwarding performance, the only major difference would be an
> extreme edge case on overburdened hardware such saving a double-lookup for IPv6
> by reverting to a single lookup for L2.

To be honest, I'm not sure why I wrote that; perhaps someone more awake 
should answer ;o)