[c-nsp] Cisco 7600 vlan issue

Saku Ytti saku+cisco-nsp at ytti.fi
Mon Dec 1 07:58:31 EST 2008

On (2008-11-30 19:28 -0500), Julio Arruda wrote:

> I was under impression the L3 forwarding and the L2 forwarding was done  
> by the same engine, in the PFC card(s) ? and behind it, the EARL for the  
> lookup and the rewriting of the header info (mac rewrite, dec ttl and  
> goes on) ?

Inside PFC/EARL you have Tycho for L3 and Superman for L2. Or 
one cost reduced version called Supertycho (with bus chip functionality
separated to dedicated chip called Kuma) in 3C and up (prolly
nexus too then).

> That is how Nortel 8600 (and earlier gen, rapidcity-legacy) did the  
> work, the same lookup engine would do l2 and l3, so I may be messing up  
> things in my mind :-), in a little more distributed fashion (more like 
> DFCs)

Dunno if this true, prolly depends how deep inside the die you look.
Also not sure what relevance there is if L2/L3 lookup is in one engine
or several engines. In my mind at least it's not advantage or disadvantage
for consumer, except for the fewer dies you have, the cheaper
it is to produce (better yields) and less power will probably
be dissimulated as heat.


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