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

[Tim Stevenson]

If you have DFC on the linecard, then *everything* is distributed for 
traffic ingress on that linecard - L2, L3, ACLs, QoS, Netflow. If 
not, then it's centrally processed by the PFC for traffic ingress on 
that linecard. There is no "local L2 switching" (or any other local 
forwarding decisions) without DFC.

Based on the description and h/w list you provided (though you didn't 
provide any linecard details), there would be zero difference in 
performance of the system for L2 vs L3.

HTH,
Tim

At 08:59 AM 6/22/2009, Phil Mayers stated:

>Jason Luke wrote:
> > I actually don't know if the linecard has a DFC. It's an old 6509 and
> > keeping any hardware information straight on this proves to be confusing
> > to me.
> > This is what I have.
> > L3 Switching Engine II  WS-F6K-PFC2
> >
> > 1000BaseX Supervisor      WS-X6K-SUP2-2GE
> > Multilayer Switch Feature WS-F6K-MSFC2
> > Switch Fabric Module      WS-C6500-SFM
> >
> > When you say "some difference," are we talking significant differences
> > here?  This is basically the singular router for the entire organization
> > (3000+ computers) so EVERYTHING flows through it. If the difference
> > might be 2 or 3 times faster, then its worth it. But if the difference
> > is marginal or a few meg per second, then its kind of irrelevant.
>
>Hmm. I'm more familiar with the sup720/PFC3 hardware than the earlier stuff.
>
>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.
>
>I can't be sure about that though - anyone know if the gigE linecards
>for sup2 switch layer2 locally?
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Tim Stevenson, tstevens at cisco.com
Routing & Switching CCIE #5561
Technical Marketing Engineer, Cisco Nexus 7000
Cisco - http://www.cisco.com
IP Phone: 408-526-6759
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