What is Local <acronym title="Policy-Based Routing">PBR</acronym>?

Policy-based routing makes routing decisions based on factors other than normal routing protocols. For example, it might be necessary to forward all <acronym title="Session Initiation Protocol">SIP</acronym> packets via a more expensive low-latency link while all other traffic use a less expensive link. In this case, a route map is applied to the incoming interface and packets are forwarded based on the policies of the route map.

Unfortunately, packets generated by the router are not subject to any policy route maps (after all there is no "incoming" interface), so policy-based routing decisions can not be applied. Generally, the router does not generate a lot of traffic, so this isn't a real concern. However, in the case of a device that terminates incoming voice calls from the <acronym title="Public Switch Telephone Network">PSTN</acronym> and puts them on the IP network, this may be a big issue.

Cisco has solved this problem with Local PBR. To enable Local PBR, use the following global configuration command:

ip local policy route-map <map-tag>

Where <map-tag> is the name of the route-map you want all packets originated by the router to be subject to.

That's all there is to it. You can verify your configuration with the show ip local policy command.

Although this issue is not strictly a <acronym title="Voice over IP">VoIP</acronym> one, it seems that this is the application most likely to benefit from Local PBR. If you're using Local PBR, how about leaving a comment describing your situation and solution?