Question : How to successfully change IP address on Microsoft Exchange

Hi, I run a network (for a school) and changed the IP address on the mail server and also changed our main DNS server to reflect the new MX IP. I get the following error message when I do the latter bit: "The associated pointer record cannot be created, probably because the reference lookup zone cannot be found." can anyone explain this message and how to resolve it - with the IP switch we have no connectivity to MX. Connected with this can you tell me what I need to change in the mail server to fit our new ISP? and how i would make those changes. Thank you

Answer : How to successfully change IP address on Microsoft Exchange

Okay. The Linksys router you have is horribly under powered for 200 users. The 1720 is a much better unit. That being said, configuring a 1720 with no experience is basically impossible. And if you don't have any Ethernet interfaces on the 1720 those could run a few hundred bucks alone. The best solution would be to pay someone to reconfigure the 1720 or replace it with a modern equivalent that already comes with Ethernet interfaces and get them to configure that.

That being said, the Linksys will work and it won't be that hard to get going. So, heres what we need to do. I will list the steps. If you have a question about the steps, let me know.

- Get 1 static IP address form your new ISP

- Enter the static IP address into the routers WAN interface

- Test that dhcp desktops are getting Internet connections

- Figure out if you are using DHCP on the router or on a server. If it is on a server disable it for now. You can play with that later once we get the Internet working properly. You can have only 1 DHCP server if you want this to work.

- Look at the DHCP settings on your router. The address range should start at or something. Take note of that.

- Assign static IP addresses to all of your servers. Make sure they are lower than the DHCP scope range noted above.

So they would look like this maybe:

mail server: mask GW DNS


Other:   mask GW DNS

- Test servers for Internet connectivity. They should be able to surf the Internet now.

- Change the DNS server settings in your DHCP properties on the router to be

-Refresh the IP on a DHCP client (desktop) and see if the new settings show up and it can still surf the Internet.

Once everything is surfing the Internet we can start getting the mail going.

- On the router we will need to forward port 25 to the mail server IP ( This may be called virtual server or something on your router.

- You need to access your External DNS (possibly your ISP) and point your MX record to the external static IP address of your router.

- You need to make sure your internal MX record points at the internal IP address of your mail server (

Thats basically it. We may have to tweak some DNS settings or Exchange settings but that should be the basics.



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