Allowing users to map domains to a subdomain by using an IP address or Host name that wont change if I move servers

Question

I'm building a service, much like http://dunked.com where users can map their domain name over their subdomain.

Example: carlcox.vibecast.com would be www.carlcox.com

The process of building this functionality is not so much the issue, what I want to understand is keeping a permanent IP address (or other alternative) that users can point their domain name to, and my server would pick up.

The issue is, I'm likely to move or upgrade my servers which will result in a new IP address.

I have no idea how to implement this now, so I don't have to tell all my users to update their IP address when my servers change.

Do I need to buy a permanent IP address that I use as a proxy, give that out to users, then forward to the current server IP addresses? Is there a service that handles this type of thing?

I'm currently using DigitalOcean (via https://forge.laravel.com) and likely to migrate to AWS EC2 (probably via Elastic Beanstalk) over time.

All I want to do is give out a single IP address (or host-name) once and not have to worry about users updating.

My service would be similar to http://help.dunked.com/customer/en/portal/articles/1954817-custom-url

Does anyone have any experience on how to correctly implement this?

Answer 1

IP address is not guaranteed to remain the same in long term because it depends on your service provider's network. A domain name will not be changed as long as you keep paying for it.

So just point your host name e.g. service.yourdomain.com to your IP address and tell your users to make CNAME records in their host file.

So that

www.clientdomain.com -> service.yourdomain.com -> [ 1.2.3.4 ]

Finally, the application on your server should observe the host in the http request and handle accordingly.