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I'm hosting a service that provides custom domains to our customers. They are given an IP address (obtained from our hosting company) and then point an A record for subdomain.companyname.com to our server. We also provide an SSL certificate so each such domain is secured that way.

Our hosting company has been suffering some quality issues lately. But with the way things are set up now, moving to another company would be extremely onerous: we'd be assigned a new block of IP addresses, and we'd have to go back to every customer and have them update their DNS A record to point to the new location.

Going forward, we're researching different ways to manage this risk. In my mind, I'm imagining a kind of DNS proxy service, where we give our customers just one IP address, and they all point to that service. The service would then map those domains to our assigned IP address. If we opted to move to a different hosting company, we would only need to go into this proxy service to update the records, and our customers would be little the wiser.

My knowledge of the DNS system is a bit less than perfect, so I'm having trouble wrapping my head around what kind of service I'm looking for.

We already have something like 200 customers setup like this, so the solution I'm looking for now would be deployed for new, incoming customers, and then be slowly migrated to the existing base.

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2 Answers 2

up vote 5 down vote accepted

What I would think that you'd want to do is maintain your DNS server with A records, then have your customers use CNAMES to point to those A records.

So in your DNS server you'd have a customer with the domain name mysite.com that you are hosting. In your DNS server you setup mysite-com.AaronVegh.com (where AaronVegn.com is your companies site). Then your customers setup a CNAME for mysite.com to point to mysite-com.AaronVegh.com. Now you can change the IP in your DNS server if you move without them having to reconfigure their DNS servers.

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With a CNAME, does the URL change after you go through the redirect? i.e. does subdomain.myclient.com/accountName become myclient.mycompany.com/accountName? Because that wouldn't be desirable... –  Aaron Vegh Apr 18 '12 at 20:13
    
Nope. The browser doesn't see any difference at all. There's an extra DNS lookup that has to be done so an extra few miliseconds the first time the user does the lookup, but after that it's cached in their ISPs DNS. Nothing changes at the browser level. –  mrdenny Apr 18 '12 at 20:15
    
Ah, cool. I'm not running a DNS server myself (my hosting company manages it). Would I be best to engage the services of a third party, and if so, would you recommend one? –  Aaron Vegh Apr 18 '12 at 20:18
    
If you use a third party that makes life MUCH easier if you change hosting providers. I wouldn't know who to recommend. I use the big evil GoDaddy for my stuff (say what you will about them, their stuff works). –  mrdenny Apr 18 '12 at 20:19

depends on details of this project solution can be from something very simple (cgi/shell/perl/php) to something more complicated... unfortunately as far as I know there is no tool that would just help you out of the box, so you may need to go custom route and do something that would fit your project.

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if you down vote you need to explain –  alexus Apr 18 '12 at 21:04
    
I'd say your answer is incredibly vague and provides absolutely no useful information. Edit: I'm not the one who downvoted –  Bigbio2002 Apr 18 '12 at 21:16
    
right, comment aimed to someone who actually did down vote, and question itself is very vague and doesn't really provide enough information to give exact answer, there are a lot of ways of going about pretty much anything, but without knowing exact requirements its hard to answer it. –  alexus Apr 18 '12 at 21:20
    
"write a custom solution" is advice that could apply to many projects. It's a boilerplate answer that doesn't address anything specific in the OP, and doesn't reflect any knowledge of the topics that the OP brought up (DNS). –  Bigbio2002 Apr 18 '12 at 21:31
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I was the initial "ninja downvoter", and have since been joined by one of my compadres I see. It's been well-discussed that downvotes don't need to be accompanied by explanations. If that were the case, the software would require it. @alexus has been around long enough to know better than to post this as an "answer". The downvote communicates that there's something wrong with the answer and in this case, I felt the answerer has been around long enough to figure out what was wrong. –  EEAA Apr 18 '12 at 23:41

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