Changing ISP's and NAT and routing

Unanswered Question
Sep 1st, 2010

We're changing IPS's and have a new block of IP's from the new ISP. While we are doing this, both are running and we need to be able to have our websites whatnot available through either ISP.

We have one router, a 2811 ISR running 2800 Software (C2800NM-ADVIPSERVICESK9-M), Version 12.4(25b).

Originally we ran like this (IP blockes changed, netmasks are the same thoug)

external interface fe0/0 - 172.24.0.210/29 - default route 172.24.0.209

This interface has `ip nat outside` defined on it

We had an IP block of 172.24.0.192/26 with which we were using static NAT entries to enable access from our customers to the services we're running, such as:

ip nat inside source static 10.10.0.201 172.24.0.195 extendable

That worked just fine, and going out through our old ISP still does. The problem is with the traffic from the new ISP.


External interface is Vlan2, the 2811 has a 4 port addon module, - 192.168.0.62/30 default route 192.168.0.61

This interface also has `ip nat outside` defined on it.

The routers default route is through the Old ISP.

From the new ISP we have the IP block 192.168.0.240/28. We added similar static NAT entries as above:

ip nat inside source static tcp 10.10.0.201 192.168.0.244 extendable

Now, traffic does come in from the New ISP and that nat translation does happen (192.168.0.244 to 10.10.0.201), however if you were to browse to 192.168.0.244, your browser would just sit there and eventually time out. I believe what is happening is that the router is sending the return traffic out the default route, which goes out to the old ISP and not back out the interface it originated from.

What we are tying to do is have the traffic that should go out throgh the old ISP go out to the old ISP, but traffic from the new circiut should go out the new circuit. This only needs to be for a month or so as we move over, what we are trying to avoid is simply completely shutting off the old one and interupting service. We don't want to load balance traffic.

Exactly how do we go about routing this?

I have this problem too.
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