VLAN Accounting

Unanswered Question
Jun 20th, 2007
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I have a customer who needs a switch which can provide statistics regarding switched VLAN flows. the scenario is as follows -


Router 1 is attached to Switch A

Switch A is trunked to Switch B

Switch B is trunked to Switch C

Switch C is attached to Router 2


Switch B is attached to Router 3


the switches are passing trunked traffic between them without having interfaces on the trunked VLANs but the customer wants to gather traffic statistics on these VLANs from the switches. the switches need at least 24 10/100/1000 ethernet ports.


It seems to me that this would be possible using Netflow and


"ip flow ingress layer2-switched"


but it appears to me that this is available only on the 45xx and larger switches.


my questions are:


am i correct in using Netflow for this?


is there another way to do this accounting?


is there a smaller switch that would support using either Netflow or another method to get these statistics.


hope i that was clear - but if not just ask!


thanks in advance!

William

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leighharrison Wed, 06/20/2007 - 06:33
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Hi there William,


You can monitor traffic flow through vlans using normal snmp.


LH


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wpinberlin Wed, 06/20/2007 - 07:08
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Leigh,

thanks for your response. Would i be able to see the layer 2 traffic statistics via SNMP despite the fact the traffic is remaining in the VLAN and being trunked through the switches?

wpinberlin Wed, 06/20/2007 - 07:29
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Leigh,

thanks for your response. Would i be able to see the layer 2 traffic statistics via SNMP despite the fact the traffic is remaining in the VLAN and being trunked through the switches?

leighharrison Thu, 06/21/2007 - 00:09
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Hi there,


If you wanted to see the traffic stats, then you would need to have a layer 3 interface in the vlan.... It shouldn't need to have an ip address though - I'm not 100% sure and I've not got any kit spare to have a test for you at the moment.


Are the only layer 3 interfaces on the routers? You might not be able to get stats for the layer 2 trunks, but you may be able to get the total from the routers interfaces, or the switches layer 3 interfaces. Also, you *could* get stats from the user ports in the vlans (it doesn't seem like there's that many) add them together for each switch and graph that, as it should give the same throughput as the uplinked trunk!


LH


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wpinberlin Thu, 06/21/2007 - 01:00
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Okay thanks, I suggested he get the statistics off the routers but for reason he doesn't want to. But thanks for your response!


~Wm

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