Different amount of AS prepends in same route-map?

[Larry Sullivan]

Can you have a different amount of AS prepends in the same route-map using match statements?  What I'm trying to achieve is having a certain IP used for MIS traffic take our backup VPN at our regional hub instead of saturating the primary MPLS.  The thought is to have the backup VPN advertise less hops to EBGP neighbors than the primary for the MIS traffic generating IP.  See below configs... Will the MIS IP be advertised with 3 prepends and all other traffic 7?  Will this work?  If not, any ideas on how to approach this?  To add more complexity, the purpose is to have the MIS traffic directed to our COLO site instead of direct VPN to the remotes receiving the MIS traffic.  This is being done so that from the COLO facility the traffic will take the primary MPLS circuits at the remotes.  On the way back, the MIS traffic needs to traverse COLO again and back to the regional remotes backup VPN, which is why I need to approach this design from an advertisement standpoint.  Essential I need one IP to prefer the backup with all others the primary.  Thanks.

ip prefix-list MIS seq 5 permit 10.100.4.41/32

route-map Secondary permit 10
 match ip address prefix-list MIS
 set metric 10000
 set local-preference 200
 set ip next-hop 172.21.169.150
 set as-path prepend 65555 65555 65555

route-map Secondary permit 20
 set metric 10000
 set as-path prepend 65555 65555 65555 65555 65555 65555 65555

[Larry Sullivan]

Francesco,

I implemented your solution and the AS prepends worked.  Thank you very much.  Great work.  My final configs for the labbed up portion are below.  (I need to do the whole 10.100.4.0 subnet in the prefix-list).

R2

ip prefix-list MIS seq 10 permit 10.100.4.0/24

!
route-map Secondary permit 10
 match ip address prefix-list MIS
 set local-preference 200
 set as-path prepend 64555 64555 64555
!
route-map Secondary permit 20
 set as-path prepend 64555 64555 64555 64555 64555 64555 64555

route-map MIS permit 10
 match ip address prefix-list MIS
 set ip next-hop 192.168.2.3

interface Vlan1
 ip address 10.100.4.1 255.255.255.0
 ip policy route-map MIS

Thanks everyone for the assistance. 

[Francesco Molino · Accepted solution]

By doing the whole /24, you will change the routing for the complete subnet, is it what you want?

If you want to do only the host 10.100.4.41/32: let's assume the interface of your local router facing the subnet 10.100.4.0/24 is g0/1

- add a static route : ip route 10.100.4.41 255.255.255.255 g0/1

- modify your prefix-list:  ip prefix-list MIS seq 10 permit 10.100.4.41/32

- Under your bgp process, redistribute your static route. If you have multiple static route and you just want to redistribute the static created previously, do:

route-map RED permit 10

 mat ip add prefi MIS

router bgp xxx

  redistribute static route-map RED

I've done a quick test to show up how you'll see it into bgp on remote peer: (the subnet I used in my example is 192.168.10.0/24)

     Network          Next Hop            Metric LocPrf Weight Path

 *>  1.1.1.1/32       172.16.255.1             0             0 1 1 1 1 1 1 1 1 ?

 *>  10.100.4.41/32   172.16.255.1             0             0 1 1 1 1 ?

 r>  172.16.255.0/24  172.16.255.1             0             0 1 1 1 1 1 1 1 1 ?

 *>  192.168.10.0     172.16.255.1             0             0 1 1 1 1 1 1 1 1 ?

 *>  192.168.10.6/32  172.16.255.1             0             0 1 1 1 1 ?

You can see that you can prepend differently your /24 and your /32

[Larry Sullivan]

Francesco,

I think I'll be good with the whole subnet.  If not, I will definitely come back and reference your solution.  Thanks again. 

[Francesco Molino]

No pb. You're welcome

[paul driver]

Hello

i see you  have separated the PBR but still have the LP applied to  the rm - which I guess if you check doesn’t work  Due to the RM set outbound  towards your vpn ebgp 

res

paul