Policy-based routing and network performance

Unanswered Question
Jan 25th, 2008


can anybody tell me if using policy-based routing impacts on data transfer speeds across the interface that has "ip policy" tied to it for policy-based routing.

Since implementing it on our network two days ago, data transfers between particular hosts across the link that has policy-based routing enabled on an interface (for other specific hosts) has deteriorated.

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Paolo Bevilacqua Fri, 01/25/2008 - 07:24

Which router model is that, which interface type the policy is enabled into, and do you have "ip cef" globally enabled, and not disabled under relevant interface ?

marksenteza Fri, 01/25/2008 - 07:36

The policy is enabled on a vlan interface on a 3750 routing-switch. The vlan interface is the vlan that represents the uplink between two sites.

Paolo Bevilacqua Fri, 01/25/2008 - 07:53

Hi, my understanding is that when features like policy routing and others, are enabled on a L3 switch, it uses the CPU instead of silicon to process packets, and this can lead to performance degradation.

You can ask in the "LAN switching forum" if anyone has experience of trouble with policy routing on L3 switch.

marksenteza Fri, 01/25/2008 - 08:06

Would configuring

# ip route-cache policy

on the interfaces help to enable fast-switching with PBR enabled ?

Paolo Bevilacqua Fri, 01/25/2008 - 08:28

Hi, "ip route-cache policy" is a router command and does not apply to L3.

The L3 switches will never do process, fast or CEF switching, only hardware or software based.

tom.gabriel Fri, 01/25/2008 - 08:41

The policy is applied to a VLAN on a 4 port WIC card and the physical interface the VLAN is on. IP CEF is enabled. 1720 is the model of the router.


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