Modify AS with IOS in transit AS

[Jose Maroto Grande]

I have IOS SRE advaced IPService.

I need to remove AS o Replace but i can not modify. The diagram is:

R1_AS1------R2_AS2 ------R3_AS3

In R2 I need to change or repalce AS1 when R2 announce the prefix to R3 which source is R1_AS1. I found informattion but i didnt find the solution. AS override dont work in this scene. I have resolved, i configured R1 routes like static in R2, after i redistribute in bgp. I dont like this solution, does someone know other solution (with ios)?

Thanks

[blau grana]

Hello Jose,

I do not think it is possible in IOS with some elegant solution for just one prefix.

If you have multiple prefixes and they can be summarized, you can configure aggregate-address under BGP proces but without as-set.

Then you can advertise to R3 just summarized prefix with only AS_R2 in AS path.

Best Regards

Please rate all helpful posts and close solved questions

[Jose Maroto Grande]

Thanks blau grana,

I knew this soluttion, i forgot to writte in my question. i dont configure aggregate because i have a problem:

R2 recevied only the prefix 10.251.0.0/16, this prefix doesnt have subnetting. the command " aggrgate 10.251.0.0 255.255.0.0 summary-only" doesnt eliminita de as-path.

Thanks

[blau grana · Accepted solution]

OK, Jose

So how about you do the opposite -> deaggregate 10.251.0.0/16 prefix and send two more specific prefixes to AS_R3.

This is what I mean:

http://blog.initialdraft.com/archives/3527/

Best Regards

Please rate all helpful posts and close solved questions

[Jose Maroto Grande]

Thanks blau grana,

It is great, this was just look up. I woul want only delete the AS-PATH of the prefix, i changed the solution, i havent splitted the prefix.

I have changed the solution with this config:

router bgp 65235

bgp inject-map INJECT--PREFIX-SIN-SUBNETTING exist-map MATCH--PREFIX-SIN-SUBNETTING

!

ip prefix-list INJECT seq 10 permit 10.251.0.0/16

!

ip prefix-list RUTAS-LEARNED-SIN-SUBNETTING seq 5 permit 10.251.0.0/16

!

ip prefix-list ROUTE-SOURCE seq 5 permit 1.1.1.1/32

!

!

!

!

route-map MATCH-PREFIX-SIN-SUBNETTING permit 10

match ip address prefix-list RUTAS-LEARNED-SIN-SUBNETTING

match ip route-source prefix-list ROUTE-SOURCE

!

route-map INJECT--PREFIX-SIN-SUBNETTING permit 10

set ip address prefix-list INJECT

!

This solution works fine.