Tuesday, July 02, 2013

Understanding PBR

All packets received on an interface with PBR enabled are passed through enhanced packet filters known as route maps. The route maps used by PBR dictate the policy, determining to where the packets are forwarded.
Route maps are composed of statements. The route map statements can be marked as permit or deny, and they are interpreted in the following ways:
•If a statement is marked as deny, the packets meeting the match criteria are sent back through the normal forwarding channels and destination-based routing is performed.
•If the statement is marked as permit and a packet matches the access-lists, then the first valid set clause is applied to that packet.

You specify PBR on the incoming interface (the interface on which packets are received), NOT outgoing interface.

pbr is looked at before routing table.

Ref: http://www.cisco.com/en/US/docs/switches/lan/catalyst4500/12.2/25ew/configuration/guide/pbroute.html