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.
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