Cisco Systems 3750E manual PBR Configuration Guidelines, 38-84

Chapter 38 Configuring IP Unicast Routing

Configuring Protocol-Independent Features

With PBR, you classify traffic using access control lists (ACLs) and then make traffic go through a different path. PBR is applied to incoming packets. All packets received on an interface with PBR enabled are passed through route maps. Based on the criteria defined in the route maps, packets are forwarded (routed) to the appropriate next hop.

•If packets do not match any route map statements, all set clauses are applied.

•If a statement is marked as permit and the packets do not match any route-map statements, the packets are sent through the normal forwarding channels, and destination-based routing is performed.

•For PBR, route-map statements marked as deny are not supported.

For more information about configuring route maps, see the “Using Route Maps to Redistribute Routing Information” section on page 38-80.

You can use standard IP ACLs to specify match criteria for a source address or extended IP ACLs to specify match criteria based on an application, a protocol type, or an end station. The process proceeds through the route map until a match is found. If no match is found, normal destination-based routing occurs. There is an implicit deny at the end of the list of match statements.

If match clauses are satisfied, you can use a set clause to specify the IP addresses identifying the next hop router in the path.

For details about PBR commands and keywords, see the Cisco IOS IP Command Reference, Volume 2 of 3: Routing Protocols, Release 12.2. For a list of PBR commands that are visible but not supported by the switch, see Appendix C, “Unsupported Commands in Cisco IOS Release 12.2(37)SE.”

PBR configuration is applied to the whole stack, and all switches use the stack master configuration.

Note This software release does not support Policy-Based Routing (PBR) when processing IPv4 and IPv6 traffic.

PBR Configuration Guidelines

Before configuring PBR, you should be aware of this information:

•To use PBR, you must have the IP services feature set enabled on the switch or stack master.

•Multicast traffic is not policy-routed. PBR applies to only to unicast traffic.

•You can enable PBR on a routed port or an SVI.

•The switch does not support route-map deny statements for PBR.

•You can apply a policy route map to an EtherChannel port channel in Layer 3 mode, but you cannot apply a policy route map to a physical interface that is a member of the EtherChannel. If you try to do so, the command is rejected. When a policy route map is applied to a physical interface, that interface cannot become a member of an EtherChannel.

•You can define a maximum of 246 IP policy route maps on the switch or switch stack.

•You can define a maximum of 512 access control entries (ACEs) for PBR on the switch or switch stack.

•When configuring match criteria in a route map, follow these guidelines:

–Do not match ACLs that permit packets destined for a local address. PBR would forward these packets, which could cause ping or Telnet failure or route protocol flappping.

–Do not match ACLs with deny ACEs. Packets that match a deny ACE are sent to the CPU, which could cause high CPU utilization.

	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
38-84	OL-9775-02