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Cisco routers running Cisco IOS supports pased based IP Routing which can route packets based on a set IP Policy exiting an Interface.

Policy based routing in Cisco ROuters can be performed by using "route-map" and then applying as a policy to the interface of the IP Packets.

The route-map  has a list of "match" and "set" commands where match defines the criteria under which the policy routing is performed (say, match a destination IP or a standard or Extended ACL) and set defines the actions to perform when match criteris met (say, set next hop).

In this example, I change the routing to a particular network only from a particular subnet which is defined in a standard ACL. This ACL is then matched in a route-map and applied as an IP policy for routing change for the change in routing behaviour.

IP Route-Map

Create Standard ACL

From the global configuration mode, create an ACL to permit source network 10.1.1.0/24

ciscorouter# conf term

ciscorouter(config)# access-list 10 permit 10.1.1.0 0.0.0.255

That creates a new ACL "10" with a permit for 10.1.1.0/24 network.

Create Route-Map

Define a route-map with "match" conditions and "set" actions.

ciscorouter(config)# route-map SetNextHop permit 10

ciscorouter(config-route-map)# match ip address 10

ciscorouter(config-route-map)# set ip next-hop 192.168.0.1

ciscorouter(config-route-map)# exit

That creates a route-map called "SetNextHop" and matches the ACL 10 where the source network for which the route-map should be actioned. I've set the action to be taken when the source network matches to set the next hop router as 192.168.0.1

Apply Policy Route-map to interface

This route-map is now applied to the interface (fa0/0)

ciscorouter(config)# interface fa0/0

ciscorouter(config-if)# ip policy route-map SetNextHop

Test for yourself. For source network 10.1.1.0/24, the nexthop IP is set as 192.168.0.1 (Router B) where every other source networks are router as specified by the static/dynamic routes (in our example through Router A)

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9 Comments so far »

  1. by mehul, on January 7 2009 @ 9:25 am

     

    nice document site for refer

  2. by joel, on April 22 2009 @ 10:03 pm

     

    int fa0/0?

    just wanna say thx..

  3. by n. tomar, on May 14 2009 @ 1:17 am

     

    really nice document.

  4. by Achilleas, on September 17 2009 @ 2:19 am

     

    I have a question.

    What is the inside IP address for router A and router B
    and
    which is the gateway for the PCs to LAN (192.168.1.0/24)

    Achilleas from Greece

  5. by aptgetmoo, on December 22 2009 @ 7:58 pm

     

    Hello.

    I would like to know, can I reroute based on source IP address instead of source network address?

    Thanks in advance.
    aptgetmoo

  6. by sunny, on June 2 2010 @ 12:04 am

     

    what is th difference when you say set ip next-hop compare to set interface ?

    I have found issue in traffic getting droped with set ip next-hop in reoute-map but worked with set interface command.

    Appreciate your input.

    regards
    Sunny

  7. by Faisal Memon, on July 14 2010 @ 5:59 am

     

    Nice Share. Much Appreciated.

  8. by Powerchino, on September 21 2010 @ 12:55 pm

     

    Thanks for sharing, your document is right on target and please keep up the good work, Thank you!

  9. by m3kw, on August 23 2011 @ 2:22 pm

     

    Didn’t you forgot the “no switchport” command?

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