[nsp] Re: Per VLAN Stats on MSFC2 - Complaints from the Field

Terry Baranski tbaranski at mail.com
Fri Nov 21 22:07:38 EST 2003

>> The reporting of the Layer 2 and 3 devices, virtual or
>> otherwise appears to be correct; I argue that Cisco attempting 
>> to 'populate' the SVI counters with information they are 
>> actually not seeing would be 'breaking' the implementation.  
>> Remember folks, we're talking about multi layer switching/routing
>> here; the SVI isn't processing all of the traffic and should not 
>> lie and say that it is.
> As mentioned before: so what?  On a flow based engine (as "old" 
> MLS is): just export the flow data from the L2 engine to the L3 
> part as soon as the flow is expired.  Not exactly rocket science.

I don't think it's unreasonable to view an SVI as a MAC address (with an
associated IP) that is used as a next-hop for packets leaving the VLAN,
and as a source for packets entering the VLAN.  Using this perspective,
I'd argue that all such packets use the SVI whether they actually hit
the MSFC or not.  Take the SVI away, and the packets stop flowing.  So
the issue with SVI counters has never made sense to me, and is a major
inconvenience when you care about traffic stats.


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