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.