[mrtg] Re: SNMP and Cisco ... Oh the Fun a newbie can have.

[Cook, Garry]

mrtg-bounce at list.ee.ethz.ch wrote:
> RE: [mrtg] Re: SNMP and Cisco ... Oh the Fun a newbie can
> have.I understand your thinking on this, but even though we
> are using MLS I should see more activity between those ports
> just because we are transferring pacs images that can be
> 50-100MB per case. So I would've imagined that we are using
> more of the bandwidth than we are possibly seeing. I am going
> to try and approach this differently, instead of monitoring
> the CoreSwitches i am going to monitor the IDF's.
> 
> Moses.

I'm not convinced that you do understand the thinking. Since you state
that you ARE using MLS, then this means that the router and the switch
are working together. Hence the ML, multi layer, router at layer 3 and
switch at layer 2. The fact is that you ARE using more of the bandwidth
than you are actually seeing. You're not just imagining this.

Once a flow or path is established, the flow is stored in a table. Then,
when the switch sees traffic, it consults the table and if it finds a
flow listed there as active, the packets are switched in hardware, not
routed in software. Therefore, there is no record or count of the
packets that can be grepped with SNMP (or any other method). The only
traffic that MRTG will see on the switch ports or VLANs is the first few
packets of a flow.

HTH

Garry W. Cook, CCNA
Network Infrastructure Manager
MACTEC, Inc. - http://www.mactec.com/
303.308.6228 (Office) - 720.220.1862 (Mobile)

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