[mrtg] Re: Two questions...

[Cook, Garry]

> Hi everyone,
> Here are my questions......
> 
[snippity-snip]
> 2)  I am having some trouble monitoring FE subinterfaces...I
> have tried
> using both the 32 bit In/Out octet counter (MRTG standard),
> and the 64 bit
> In/Out HC octet counter.  The 32 bit does not return accurate
> data and the
> 64 bit returns nothing.  Does anyone know how I can monitor
> FE (or VLAN)
> subinterfaces accurately?  These interfaces are configured on
> Cisco routers
> that support both SNMP V1 and V2.
> 
> Thanks for the assistance!!!
> Rebecca

Are you using multilayer switching on this device? If so, the VLAN data
is probably accurate, although not necessarily showing you what you
think that it should. When using MLS, the first packet in a flow is
compared to the cache and if it passes muster, packets from this flow
are switched in hardware from that point forward. These packets are
therefore not counted/accessible via SNMP. I know that this is a fairly
simple description, but I believe that this is a Cisco issue, not
something that can be addressed with MRTG. You may need to use NetFlow
or NBAR to get graphs that look the way you expect.

If you're not using MLS, then what leads you to believe that the MRTG
polled data is inaccurate?

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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