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Prepending specific subnets

I am trying to prepend specific subnets that I am advertising. What is the best method to do this with these 3 options? Basic route-maps, route-maps with continue statements, or route-map with policy lists. What other valid options do I have?

Will this work with basic route-maps?

Route-map continue command? It is only supported on a few versions of IOS all of which I?m not currently running.

Policy list? Kinda confusing with Cisco?s statement that ?Policy lists support only match clauses and do not support set clauses. However, policy lists can coexist, within the same route map entry, with match and set clauses that are configured separately from the policy lists.?

Any suggestions are appreciated, thanks!



Re: Prepending specific subnets


If you want to have a simple and clear configuration , then it would be better to go with a route-map .

As we have many features available with the route-map and your requirement is only for matching some specific subnets , it would be better to use the route-map , so that during troubleshooting time also you will not have mcuh to check.

Hope this helps


vanesh k

Re: Prepending specific subnets

Route map is the best option here as it offers you lot of features.

sample config in which u advertise one subnet with prepend

router bgp 100

network mask

network mask

neighbor remote-as 200

neighbor route-map map1 out

access-list 1 permit

access-list 2 permit

route-map map1 permit 10

match ip address 2

set as-path prepend 100 100 100 100 100

route-map map1 permit 20

match ip address 1

HTH, rate if it does