7.2 Policy Routing
7.2.2 Policy routing example
Figure presents a policy-routing scenario. You can use a route map at RTA to implement policy routing. Assume for this example that the policy you want to enforce is as follows: Internet-bound traffic from 192.168.1.0 /24 is to be routed to ISP1, and Internet-bound traffic from 172.16.1.0 /24 is to be routed to ISP2.

First, define the access lists that will be used in the route maps to match IP addresses; then configure the route map itself using the syntax shown in Figure .

The commands in Figure have actually configured two policies. The ISP1 route map matches access list 1 and routes traffic out S0 toward ISP1. The ISP2 route map matches access list 2 and routes that traffic out S1 toward ISP2.

The final step is to apply each route map to the appropriate interface on RTA using the ip policy route-map command, as shown in Figure . With the route maps applied to the appropriate LAN interfaces, policy routing is successfully implemented.

Frequently, route maps are used to control the exchange of routing information during redistribution. Route redistribution is detailed in the next section.