Configure Custom Domains in Windows Azure

So you've decided to call your web app up from the minors and into the big leagues to Windows Azure. Among other things with this move from the country to the big city you might be wondering, "How do I change the friendly DNS that Azure has graciously assigned my app to the even friendlier domain I already have?"

Meat & Potatoes

You've got your friendly, assigned DNS from Azure - friendlyappname.cloudapp.net ("friendlyappname" being replaced by your actual DNS name). At 50,000 feet, Azure assigns this DNS to your application as a layer of abstraction provided that the Virtual IP addresses (VIPs) of the application change and will prevent any disruption of service. Given this change, Azure is smart enough and will do the leg work of updating its DNS to properly map the new VIPs to the DNS it assigned your application.

Where does this leave you?

Putting It Together

Since there is the chance that the VIPs change you can't assign an A record to a specific IP for your domain. You'll have to settle with registering a CNAME. I won't cover what a CNAME is but in the event that this is Greek to you please collaborate with your infrastructure team and/or your domain's registrar to get these details.

Create CNAME Record

Still cruising at 50,000 feet, what you'll want to do first is create a CNAME mapping "www" subdomain to your Azure assigned name.

Forwarding the Root Domain

Now you'll want to use domain forwarding to map the root domain (myownfriendlierdomain.com) to the mapped subdomain (www.myownfriendlierdomain.com).

Things That Go FAIL

CNAME records need to map to a specific subdomain: they can't map to the root domain. "www" was used above, but maybe you're application is a forum, you could use "forum".

Secondly, do not wildcard map - "*.myownfriendlierdomain.com".

Summary

1. It is possible to configure DNS to an application in the cloud.
2. VIPs can change and the Azure assigned DNS name abstracts this to prevent any interruption in service.
3. A record to specifc IP is not possible because of VIPs.
4. CNAME is the answer.
5. Create CNAME mapping - "www", "forum", "blog", et. al.
6. Forward root domain to mapping - "www.myownfriendlierdomain.com", "blog.myownfriendlierdomain.com", et. al.
   
7. Always map to subdomain, CNAME cannot map to root levels.
8. No wildcard mappings.

Cheers!