DNS update to resolve external address as internal IP

Question

This should be a simple one:

We have an inhouse mail server, so our outlook users hit it locally.. mailserver.mydomain.local

But smartphone and laptop users need to be able to hit it from inside and outside. I assume that a simple solution is to set up laptops and smartphones to hit the external address mail.mydomain.com and then set a record on my internal DNS server to resolve mail.mydomain.com to its local IP address.

Is this an effective solution, and can you tell me how I would set it up in (windows server 2008 R2) DNS?

Answer 1

We use the exact set up in multiple sites.

External - Log into your domain control panel and set up your domain DNS with an A Record for mail (mail.mydomain.com) that points to your server's static IP. eg 92.27.xxx.xxx

Internal - Open DNS managment. Expand Server>Foward Lookup Zones. Add a forward lookup for mail.mydomain.com that has an A Record for the mail server's static IP. eg 192.168.xxx.xxx

We have never had any complaints from anyone about any server access glitches due to them leaving the office etc. Works on laptops and smartphones. Just ensure that the DNS server on the wireless routers/hubs/switches is the Windows Server 2008 box, otherwise nothing will resolve.

Answer 2

That solution has one drawback: DNS answers are cached, usually for several hours. This causes a situation where users will not really be able to navigate back and forth between internal and external domains.

The typical solution is to setup a relay server that can be reached both internally and externally with the same IP address.