[mrtg] Re: Stating a Gig Ethernet Port

David Grohmann grohmann at arlut.utexas.edu
Tue Aug 22 17:37:12 MEST 2006

John Williams wrote:
> We have a 7304 that has an uplink on it’s Gig Ethernet port but are seeing
> some strange MRTG stats.
> The MRTG graph is up and down like a yoyo, one minute it shows the
> input/output at around 121Mb 5 minute average, and the next it’s dropped to
> around 8Mb 5 minute average.
> At first I thought it maybe something wrong on the 7304, but upon looking at
> the interface stats on the router the 5 minute output/input rate is always
> over 100Mb.
> I’ve confirmed with our upstream that the Gig port connects to and they see
> us never doing less that 100Mb.
> So I’m not sure where the problem is.
> I run Snmpwalk independently from the command line to see what Octets are
> reported back from the router and sure enough one minute it says over 100Mb
> the next as low as 8Mb.
> I was wondering if anyone else has seen this behaviour from SNMP on a 7304
> router.
> The IOS we have on the router is c7300-js-mz.122-28.SB3 which is the latest
> version from the Cisco site.
> I’ve looked at bug reports for this IOS and see nothing that relates to SNMP
> reporting.
> We’ve tried the uplink of a different port and still get the same results.
> The interface reports over 100Mb 5 minute average but MRTG graphs show it up
> and down from 8Mb to over 100Mb.
> Is it the IOS, the Gig ports, SNMP??
> Not sure where to look now.
> Thanks for any help you can supply.
> John
It sounds like you are querying  the 32 bit counters instead of th e64 
bit counters, and they are rolling over  in less than 5 minutes,  an 
easy thing to do with gig-E.

We have had the same problem, for some reason Net-SNMP doesn't present 
64 bit counters for anything, only 32 bit counters. Does anyone know why?

David Grohmann
Senior Student Associate
Applied Research Lab : UT Austin : ESL - S206
Office: 512-835-3237
Cell: 210-861-6882

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