[c-nsp] Local-switching on DFC's?

[David Sinn]

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Depends on what ports.

If the ports are on the same fabric channel, then they can locally  
switch.  So for a 6704, ports 1 & 2 will locally switch as will ports  
3 & 4.  But traffic between 1 or 2 going to 3 or 4 and vice-versa  
must traverse the fabric.  6748's are also split between two fabric's  
just 24 ports in a cluster.  6708's _should_ locally switch for the  
first four ports and again for the last four ports, but will utilize  
the fabric to get between port sets.  I don't have a 6708 yet, so I  
can't confirm that one.

Multicast complicates things, but I'm assuming the bulk of your  
question is for unicast.

DFC's just localize the lookup.

David

On Sep 27, 2006, at 10:18 AM, Kevin Graham wrote:

> I had been under the impression that DFC's hairpinned traffic off the
> fabric interfaces for local traffic and were still constrained by  
> fabric
> speed for forwarding (ie. between two ports on the same module  
> still eats
> fabric bandwidth for that module).
>
> Reading some of the press on the 6708 (Cisco's press release doesn't
> have much detail), there's mention that it handle 64gb/s locally:
>
>   http://www.networkworld.com/news/2006/092506cisco10g.html?zb&rc=lan
>
> Has this always been the case, or is this something new to the DFC3C?
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