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Community Member

Monitoring VLAN traffic

I moved from 2500 series routers to a switched network using a Catalyst 3750 and 3560 switches over the course of the last year. In my routed network I used MRTG to monitor traffic on my interfaces. In my switched network environment I have not been able to find a free or low cost tool that will monitor VLAN traffic. Any suggestions?

4 REPLIES
Community Member

Re: Monitoring VLAN traffic

Have you tried MRTG with your switches? It's a long time since I've used MRTG but I seem to remember that it showed stats for the VLAN interfaces as well as the physical interfaces..

Community Member

Re: Monitoring VLAN traffic

Yes, we tried MRTG and could not get it to see VLANs, only physical interfaces. If there's a way to do this in MRTG I'd love some help in configuring it to work for us!

Community Member

Re: Monitoring VLAN traffic

Sorry for the confusion....I've just checked our old MRTG system and it doesn't show VLAN stats.

Can't see a what of doing this sorry?

VLAN interfaces are identified in CiscoWorks but I'm not sure what (if any) stats are collected or how you would get to them..

Perhaps some of the CiscoWorks experts on here will have some ideas?

Community Member

Re: Monitoring VLAN traffic

I have the same problem and found these links that provided answers:

http://forums.cacti.net/about29656.html&highlight=
http://www.experts-exchange.com/Hardware/Networking_Hardware/Switches/Q_23738165.html

Vlans on 3560s, 3750s and 3550s do not show stats.  The packets are forwarded with the ASIC chips and do not cross the CPU for actual processing.  To actually see the traffic you will need to turn off CEF, which decrases the performance significantly (not recommended, see links above).

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