ISP Switch, Multiple Gateways

Unanswered Question

I am prepping for an ISP switch, and am wondering if it is possible to have a seamless switch.

Lets say I have an internal host,, that is behind CurrentFirewall that handles CurrentISP's range of The firewall is configured to pass to internal host Now NewFirewall handles address range from NewISP and is configured to pass to So the big question is once DNS is switched, if a client is still resolving the old public IP of, will the inside host be able to handle said clients requests?

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oj88 Thu, 03/29/2007 - 00:20
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I believe this will work. We've done it with forwarding SMTP from two different ISPs and routers to the same internal server. The routers are doing NAT as well as the firewall.

What you can do is try accessing 209.2.26 and from the Internet and see if the the server will respond.


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