ISP Switch, Multiple Gateways

benhanson · ‎03-28-2007

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, 192.168.0.10, that is behind CurrentFirewall that handles CurrentISP's range of 209.1.1.64/28. The firewall is configured to pass 209.1.1.66 to internal host 192.168.0.10. Now NewFirewall handles address range 209.2.2.1/27 from NewISP and is configured to pass 209.2.2.6 to 192.168.0.10. So the big question is once DNS is switched, if a client is still resolving the old public IP of 209.1.1.66, will the inside host be able to handle said clients requests?

oj88 · ‎03-29-2007

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 209.1.1.66 from the Internet and see if the the server will respond.