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Reliable static route with NAT

I have a 2851 router with two WAN links to two different ISPs. There is one LAN subnet that's on a private IP range and is using dynamic NAT (overload) to connect to either ISPs.

I have gone as far as configuring NAT and reliable static route but are having problems, namely:

1. If ISP1 fails, traffic doesn't go to ISP2 because the dynamic NAT entries are still pointing to ISP1. The admin has to do a clear ip nat translations * to be able to use ISP2.

2. If I change the NAT translation timeouts from default to say a few seconds, I can get it to failover to the other ISP in a few seconds. However, even if ISP1 or ISP2 is stable, Citrix and Yahoo Messenger keeps on disconnecting. I'm guessing that the dynamic NAT entries are being refreshed every few seconds, causing some applications to lose connectivity.

My question is, is there a way to flush all dynamic NAT translations whenever reliable static route kicks in to use the alternative ISP?

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