Monitoring L3 vlan traffic on Cat6500 using MRTG

[adventurer]

Hi, Does anyone has experience in monitoring of L3 vlan traffic on Cat6500 using MRTG ? Somehow my graphs look abnormally low.

Regards.

[David Stanford]

What variables are you using to monitor traffic? If you are using snmp, are you using community string indexing?

ex) public@100 would give stats for vlan 100

[adventurer]

I have not customised it yet. All i did is to follow the guide:

perl cfgmaker public@10.10.10.1 --global "WorkDir: c:\www\mrtg" --output mrtg.cfg

perl mrtg mrtg.cfg

This will generate the graphs for all vlan interfaces. In all of the graphs, the traffic is exceptionally low, kind of strange.

Regards.

[dave.keith]

I believe that if you are looking at the VLANs L3 interface then you will only see the initial packets that are 'routed'. All subsequent packets are 'switched' using CEF and these packets do not ever hit the VLAN L3 interface. This may be why you see very little traffic on those interfaces.

Dave

[adventurer]

This is what i'm afraid of.

But on the other hand, all routers do the same CEF isn't it ? Then why does MRTG works well with routers but not L3 switches ?