Forward packet based on input interface

[juanmc]

Hello,

I have a 2911 router connected to two different ISP. Is it posible to route traffic based on what interface the traffic came first?

I'll try to explain. Lets say I have the deault route to use interface gig0/0(ISP1),  but a certain ip packet reach the router by interface gig0/1(ISP2). Is there any way (if possible without using source NAT) that I could route traffic back to that ip address using interface gig0/1. The source Ip addresses are not fixed, so I can not use Policy Based Routing.

Thank you.

[paolo bevilacqua]

That is only possible using NAT. Otherwise the router does not keep track of original interface for packets "going back".

[George Mason]

I have exactly the same issue, on a different router. Cisco 1801 with two Dialer interfaces, one using the inbuilt ADSL interface and the other via the eth0.

I use reliable redundant routing to select an appropriate default route depending on the state of the two dialer interfaces, but whilst the primary is up, the secondary is not accessible (you get an asymmetric route - in via Dialer0 and out via Dialer1)

It seems there's no way to fix this which is a shame!