Policy-based routing
is a process whereby the device puts packets through a route map before routing
them. The route map determines which packets are routed next to which device.
You might enable policy-based routing if you want certain packets to be routed
in a certain way other than the obvious shortest path. Possible applications
for policy-based routing are to provide equal access, protocol-sensitive
routing, source-sensitive routing, routing based on interactive versus batch
traffic, and routing based on dedicated links. Policy-based routing is a more
flexible mechanism for routing packets than destination routing.
To enable
policy-based routing, you must identify which route map to use for policy-based
routing and create the route map. The route map itself specifies the match
criteria and the resulting action if all of the match clauses are met.
To enable policy-based routing on an interface, indicate which
route map the device should use by using the
ip policy route-map
map-tag command in interface configuration mode. A
packet arriving on the specified interface is subject to policy-based routing
except when its destination IP address is the same as the IP address of the
device’s interface. This
ip policy
route-map command disables fast switching of all packets arriving
on this interface.
To define the route
map to be used for policy-based routing, use the
route-map
map-tag
[permit] [sequence-number] global configuration command.
To
define the criteria by which packets are examined to learn if they will be
policy-based routed, use the
match ip address {access-list-number |
access-list-name}
command or both in route map configuration mode. No match clause
in the route map indicates no packet match.
To display the cache
entries in the policy route cache, use the
show ip cache
policy command.
![](https://www.cisco.com/content/dam/en/us/td/i/templates/note.gif) Note |
PBR is supported
only in a video template.
|