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Unable to configure netflow on Layer 2 gigabit interfaces on a Catalyst 6500 series switch that runs Cisco IOS system software

Core issue

After you enter all netflow commands, you get flows from VLAN interfaces, but cannnot get flows from physical interfaces.

Resolution

Netflow by default does not show statistics for traffic that goes across the same VLAN, but only for traffic that comes in from one VLAN and out to another Layer 3 interface, when those interfaces have the ip route-cache flow command configured individually.

If you want to enable netflow for ingress bridged traffic, use the ip flow export layer2-switched vlan {vlan id} command.

Beyond this feature, there is no support to enable netflow on a Layer 2 interface in an isolated manner.

Hence, regular netflow does not show traffic that goes within the same VLAN. It must pass through the Layer 3 interface to be caught by the netflow process. This displays statistics for traffic that goes within each VLAN, through the switch, for example, bridged traffic, in addition to routed traffic.

Refer to these documents for more information:

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    Last update:
    ‎06-22-2009 03:34 PM
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