PBR with IP SLAs

[ricardolainez]

Here's the situation, I hope someone can help me with this.

I'm implementing PBR on a multihomed network with 2 ISPs. ISP1 is the preferred exit to the internet, while ISP2 is used only for backup purposes.

There is however low priority traffic from a certain IP address range that I would like to always forward to ISP2, as long as ISP2 internet connection is functioning properly.

In order to monitor ISP2 I configured an IP SLA to ping the DNS server, but I found that I can't associate a track when setting a default next-hop in the route map. I can only associate a track when issuing the set ip next-hop command, but this means the policy would be applied to all traffic coming from the low-priority address range, and not only for traffic to unknown destinations, so traffic to destinations within the local network would be subjected to this policy, and forwarded out the wrong interface.

How could this be resolved? Thanks for your help.

[cadet alain]

Hi,

the difference betwenn set ip next-hop and set ip default next-hop is:

1) set ip next-hop: traffic will always be PBR'd and will take this next-hop

2) set ip default next-hop: traffic will only be PBR'd if there is no next-hop in the Routing Table.

So with  first set command trafffic matching the ACL will always be PBR'd and I think that's what you want, no ?

Regards.

Alain

[ricardolainez]

Well, the thing is traffic should only be PBR'd when its for unknown destinations (using default next-hop), meaning when it's going to take a default route, cause this would be internet traffic. Traffic for known destinations would be local and should not be PBR'd because it would be sent out an exit to the internet when its destination is inside the local network.

[cadet alain]

Hi,

Could you post a topology to help better understand your need and did you understand the difference between ip default next-hop and ip next-hop as I explained above ,

Regards.

Alain