[mrtg] Cisco switch backplane traffic

Starkweather, Mike mike.starkweather at anheuser-busch.com
Fri Apr 5 22:06:25 MEST 2002

I am trying to monitor backplane traffic in some of our core Catalyst switches.
We are trying to answer the question about whether we can add more devices to
these switches without danger of overloading them.

The information below is from Cisco's web site and is for the Catalyst 5000, but
seems to work for the 65xx series as well.  Everyone is responding on the .1.1.8


> Cisco's documentation indicates that sysTraffic (. is
> the OID to watch for backplane utilization.  I was unable to find any
> instances of the multiple backplane values on the core switches.  I have setup
> an MRTG to track this on the ten core switches.  If this proves to be a useful
> metric, we will probably add it to the template for the switches.
For traditional Cisco switches that have a single backplane such as the Catalyst
5000 series, sysTraffic from the CISCO-STACK-MIB provides the system backplane
utilization. The sysTraffic measurement equates roughly to the meter of the same
name on the supervisor card. 
	sysTraffic OBJECT-TYPE 
	SYNTAX Integer (0..100) 
	MAX-ACCESS read-only 
	STATUS Current 
	DESCRIPTION "Traffic meter value, i.e. the percentage of bandwidth
utilization for the previous polling interval." 
	::= { iso(1) org(3) dod(6) internet(1) private(4) enterprises(1)
cisco(9) workgroup(5) ciscoStackMIB(1) systemGrp(1) 8 } 
For switches that contain multiple backplanes, such as the Catalyst 5500, use
the sysTrafficMeterTable from the CISCO-STACK-MIB. 
	sysTrafficMeterTable OBJECT-TYPE 
	DESCRIPTION "The system traffic meter table. This table lists the
traffic meters available in the system." 
	::= { iso(1) org(3) dod(6) internet(1) private(4) enterprises(1)
cisco(9) workgroup(5) ciscoStackMIB(1) systemGrp(1) 32 } 


However the numbers are very low.  


We suspect that the peaks are backup traffic at night.  The backplanes are 32
gbps full duplex, or 16 gbps each direction.  1 percent of that is 160 mbps
which is a lot of traffic, but we thought there might be more considering the 3
or 4 to 1 oversubscription we are running on the switches (total bandwidth of
all active ports is 3 to 4 times the bandwidth of the backplane).

Has anyone tried this?  Is there a better approach?  Other variables to watch?

Mike Starkweather

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