Configuring Policy-Based Routing; Pbr Configuration Guidelines - Cisco Catalyst 3750 Software Configuration Manual

Configuring Protocol-Independent Features

Configuring Policy-Based Routing

You can use policy-based routing (PBR) to configure a defined policy for traffic flows. By using PBR,
you can have more control over routing by reducing the reliance on routes derived from routing
protocols. PBR can determine and implement routing policies that allow or deny paths based on:
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You can use PBR to provide equal-access and source-sensitive routing, routing based on interactive
versus batch traffic, or routing based on dedicated links. For example, you could transfer stock records
to a corporate office on a high-bandwidth, high-cost link for a short time while transmitting routine
application data such as e-mail over a low-bandwidth, low-cost link.
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.
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For more information about configuring route maps, see the
Information" section on page
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, or if the route map is a deny, 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.
Note For details about PBR commands and keywords, refer to the Cisco IOS IP and IP Routing Command
Reference for Release 12.1.

PBR Configuration Guidelines

Before configuring PBR, you should be aware of this information:
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Catalyst 3750 Metro Switch Software Configuration Guide
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Identity of a particular end system
Application
Protocol
If packets do not match any route map statements, all set clauses are applied.
If a statement is marked as deny, packets meeting the match criteria are sent through normal
forwarding channels, and destination-based routing is performed.
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.
28-90.
To use PBR, you must first enable the PBR template by using the sdm prefer routing-pbr global
configuration command. PBR is not supported with the routing, VLAN or default template. For
more information on the SDM templates, see
VRFs are not compatible with the PBR template. Therefore, multiprotocol label switching virtual
private networks (MPLS VPNs) and multi-VRF CE are not compatible with PBR.
Multicast traffic is not policy-routed. PBR applies to only to unicast traffic.
You can enable PBR on a routed port or an SVI.
Chapter 28
"Using Route Maps to Redistribute Routing
Chapter 6, "Configuring SDM Templates."
Configuring IP Unicast Routing
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