nat and asymmetric routing

Apr 23, 2007 2 Replies
L
nat and asymmetric routing open original image

Is it possible to nat outbound (using same addresses) out a different interface than the incoming interface? The lan default gw is on the preferred outbound path so traffic would have to reflect off that int and get natted. The ISP for the outbound path is partnered with the service provider providing the inbound path so they'll honor the "foreign" block.



thanks



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H

I'm not sure if I understand your question correctly, but most likely you need a feature named "nat on a stick". It allows you to do NAT translation to a packets BEFORE they hit the "outside" interface.

Briefly, how it works:

  1. You create a loopback interface, configure it with IP address, and define as "ip nat outside"
  2. You create PBR (policy based routing), to send a packets to loopback interface.
  3. After packet hits a loopback interface, and get NATed, packet gets back to a routing engine to be routed normal way.
  4. You create another PBR for returning traffic.

Good luck,

Mike CCNP, CCDP, CCSP, Cisco Voice, MCSE W2K, MCSE+I, Security+, etc. CCIE R&S (in progress), CCIE Voice (in progress)

------ Headset Adapters for Cisco IP Phones

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L

Thanks mike. That's what TAC suggested as well. Pretty clever.

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