Policy-based routing allows you to configure a defined policy for IPv4 traffic flows, lessening reliance on routes derived from routing protocols. All packets received on an interface with policy-based routing enabled are passed through enhanced packet filters or route maps. The route maps dictate the policy, determining where to forward packets.

Route maps are composed of match and set statements that you can mark as permit or deny. You can interpret the statements as follows:

• If the packets match any route map statements, all the set statements are applied. One of these actions involves choosing the next-hop.

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

For more information, see the Route Maps section.

Policy-based routing includes the following features:

• Source-based routing—Routes traffic that originates from different sets of users through different connections across the policy routers.

• Load sharing—Distributes traffic among multiple paths based on the traffic characteristics.

Policy-based routing has the following prerequisites:

• Install the correct license.

• You must enable policy-based routing (see the Enabling the Policy-Based Routing Feature section).

• Assign an IP address on the interface and bring the interface up before you apply a route map on the interface for policy-based routing.

Policy-based routing has the following configuration guidelines and limitations:

• A match command cannot refer to more than one ACL in a route map used for policy-based routing.

• An ACL used in a policy-based routing route map cannot include a deny statement.

• The same route map can be shared among different interfaces for policy-based routing as long as the interfaces belong to the same virtual routing and forwarding (VRF) instance.

Use the show route-map rmap-name pbr-statistics command to display the statistics for policy-based routing. The statistics are maintained for each route-map sequence. It shows the number of packets that are policy-routed based on the match condition in a given route-map sequence. All other packets that are routed using the default routing table (could be due to unreachable next-hops in the set command) are also displayed. The PBR statistics collection must be turned on before any statistics can be shown.

This example shows how to display PBR statistics:

switch(config)# show route-map pbr-sample pbr-statistics

Use the clear route-map rmap-name pbr-statistics command to clear the counters maintained for PBR statistics of a route-map.

This example shows how to clear PBR statistics:

switch(config)# clear route-map pbr-sample pbr-statistics

This example shows how to configure a simple route policy on an interface:

feature pbr
ip access-list pbr-sample
permit tcp host 10.1.1.1 host 192.168.2.1 eq 80
!
route-map pbr-sample
match ip address pbr-sample
set ip next-hop 192.168.1.1
!
route-map pbr-sample pbr-statistics
 
interface ethernet 1/2
ip policy route-map pbr-sample

The following output verifies this configuration:

n3000# show route-map pbr-sample
 
route-map pbr-sample, permit, sequence 10
Match clauses:
ip address (access-lists): pbr-sample
Set clauses:
ip next-hop 192.168.1.1
 
n3000# show route-map pbr-sample pbr-statistics
 
route-map pbr-sample, permit, sequence 10
Policy routing matches: 84 packets

The following topics can give more information on Policy Based Routing:

• Configuring Route Policy Manager

For additional information related to implementing IP, see the following sections:

• Related Documents

• Standards