Policy Base Routing with IP verify unicast reverse path

Unanswered Question
Jul 1st, 2007

Dear Expert,

recently i was configure the policy base routing on router, but over the interface i had put in "ip verify unicast reverse path", when put in this command over the serial interface, the traffic will drop. does anyone facing this problem before? After remove this command the traffic will pass-thru. Just wondering why the IP verify unicast reverse command will affect the PBR.

I have this problem too.
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milan.kulik Mon, 07/02/2007 - 00:00

Hi,

just guessing:

If you need PBR, it probably means you are sending the traffic to a different interface than your routing table is pointing to.

And the returning traffic is also coming from that interface?

If yes, the "IP verify unicast reverse path" works correctly dropping this traffic.

BR,

Milan

laitonglek Mon, 07/02/2007 - 16:57

Dear Milan,

Thanks for the information, and i have another question, if let say the PBR is take place before the routing process, beside using show route-map or show access-list to see whether the traffic hits or not, any other command we can looks for the more details, because sometimes we dont have statistics to guarantee that the PBR we have done is guarantee workable.

thanks.

Edison Ortiz Mon, 07/02/2007 - 05:10

The "ip policy route-map [policy-name]" command should be placed in the ingress interface (before any routing decision takes place) and the "ip verify unicast reverse path" should be placed in the egress interface (traffic that didn't leave the interface shouldn't be allowed to come back via the interface).

srimural Mon, 07/02/2007 - 07:34

Hi Edison,

Thanks alot for the explanation.

Thanks and Regards,

Srinath.M

Cable&Wireless

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