still confused about exchange 2003 - 2010 exchange DNS


per the title, I was hoping someone could verify the following DNS entries for my exchange 2003 - 2010 coexistence period. While also posting any others I may need.

-Internal DNS

a record - = IP of CAS array (right now it is just the IP of one of my two exchange servers hosting CAS, HT, and MBX roles since I don't have a load balancer yet and will be setting up a DAG soon)

a record - = CAS array IP again

a record - = IP of exchange 2003

now, the records above were taken from technet forums. However, shouldn't my entries be .local since that is how we are set up? We don't use .com internally.

-External DNS

a record - = change from 2003 IP to 2010 IP?

a record - = 2010 public IP

a record - = 2003 public IP

what do I do with my MX record ( at this point? It currently points to the 2003 server. Do I change it to the 2010 server's public IP?

Will users be disconnected from their mailboxes and not get mail on mobile devices during and after applying these changes?

Please inform me if I am missing something. I have already configured the routing groups between 2003 and 2010 and mail flows fine. I moved one test account from 2003 to 2010 and am able to send and receive emails both internally and externally as well as being able to login to OWA internally.

Thanks a lot.
king daddyAsked:
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Simon Butler (Sembee)ConsultantCommented:
You can point the SMTP traffic at the new server whenever you like. I usually do it when the old server is handing off more than it is keeping.

Remember that Outlook Anywhere and ActiveSync use the same port as OWA, so if you move that you need to be sure that everything is ready to go.

Simon Butler (Sembee)ConsultantCommented:
Exchange handles the email delivery.
Therefore you can switch the MX record at any point. Internal clients will not be affected.

You can use the IP address of the CAS array for other things, but don't use the host name. The CAS Array should be used for TCP MAPI traffic, internally only.

External mailboxes should continue to work if you point them to Exchange 2010. That is because it will proxy to the Exchange 2003 server.

king daddyAuthor Commented:
Thanks Simon. So the DNS entries I posted are correct? I am sure I need to change the internal DNS entries to .local though.

When I need external clients  / mobile devices to connect to 2010, that is when I change the MX record to point to the 2010 server, correct? After I do so, will iPhones / iPads and android devices reconnect automatically? If some users are on 2003 and some are on 2010, if I point MX to 2010, mailboxes on 2003 will be accessible through 2010, correct?

thanks again
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Simon Butler (Sembee)ConsultantCommented:
MX records have nothing to do with the clients connecting - unless you are using the same host name for everything.
Have you read the coexistance documentation on Technet?
The usual method is to have two URLs - and Both are exposed to the internet with an SSL certificate. All traffic goes to Exchange 2010 and Exchange sorts out where it needs to go.

MX records are for SMTP only - and you can point those at either server. Exchange will sort out delivery.

king daddyAuthor Commented:
thanks for clarifying the MX record info. I will have two URLs, and I think I can add to my smart host account with the 2003 IP and then change the IP to that of the 2010 server.

found info, including a link to split DNS config on your website that I think I will need to follow to add .com instead of .local to make the wilcard cert and DNS records easier to deal with.

I feel like I am almost done but just can't grasp the DNS side of this migration.

Thanks again
king daddyAuthor Commented:
sorry I didn't get back to this yesterday. I read some coexistence info but became more confused with information overload. Thanks for the info, especially regarding the MX record.

I planned on pointing to my 2003 server and pointing to the 2010 server (it currently points to the 2003 server). I just got a wild card cert from go daddy, generated from the 2010 server. I am going to import that on both the 2010 and 2003 servers, then assign services.

Traffic is going out of the 2010 server now. to have it receive, I'll need to update the MX record with the 2010 server's public IP. Not sure when to actually change that.

My priority is to get DNS configured correctly, while also having a seemless mobile device transition. I am no able to touch all the mobile devices (mainly ipad / iphones) in order to connect to the 2010 server. I need to figure out the split-DNS since we use .local. I did get a post from you a while back with a link to your website's article on split DNS that I need to check out.

Any further direction, or a step-by-step, to accomplish this is greatly appreciated.

thanks again
Simon Butler (Sembee)ConsultantCommented:
As long as you have the same host name that is in the devices going to Exchange 201 and matches the SSL certificate name, then thigns will continue to work. It is when you change things that it breaks.

king daddyAuthor Commented:
so when should I point to the new 2010 server? I was going to move mail to the 2010 server after I had moved all mailboxes and also updated the MX record to point to the 2010 server. we also have webmail, and it isn't being used, so I was going to point that to 2010 now in order to test. Or should I point mail to 2010 after I successfully test with webmail?

I set up the split DNS zone using .com and there were no issues. At least none that I have yet seen.

king daddyAuthor Commented:
thanks. That's when I will do it.

I will double check OWA, active sync and outlook anywhere.

One issue that just came up with the split DNS was users could not get to using rdp or IE. I created an A record in DNS, replicated, and then they were able to connect.

Anyway, I am going to test with webmail pointing to 2010 and leave mail pointing to 2003 until I change SMTP traffic to 2010.

Thanks as usual for you assistance.

I am going to post another question soon about public IPs and two exchange server in the same site. Please look out for it.
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