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We currently have a Classic VM whose IP is directed by the DNS subdomains app.mydomain.com and api.mydomain.com. The IIS server has configured the sites app.mydomain.com and api.mydomain.com. Any user in the internet can visit both sites.

The goal is to migrate to another VM, basically creating a replica, creating two DNS subdomains app2.mydomain.com and api2.mydomain.com pointing to the new VM's IP address. As a result, visiting https://app2.mydomain.com should result in the same exact experience but be served from the new VM. Once all is tested, we would just redirect the DNS of app.mydomain.com to the new machine.

This is in theory because the IIS sites in the new VM are still called app.mydomain.com and api.mydomain.com, which will probably conflict with the domain name (app2, api2).

Are there any best practices for migrating VMs this way? There is no database involved (there is, but on a different server)

daniel p
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  • Please learn that "domain names" and "DNS" are different things so you shouldn't wrongly type "DNS" everywhere. I don't see any conflict from your current migration plan, except that by switching records in DNS the traffic will simultaneously land on both VMs for a while due to propagation delay but that's unavoidable. If you have any concern, set up a third VM and migrate app2 and api2 there to test your theory. – Lex Li Nov 29 '22 at 16:41

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IIS supports multiple host headers, so you can just add your new name to the sites on your old server alongside the existing one. The host headers in IIS have no impact on DNS and the DNS entry for the old name will still point to the old server.

Sam Cogan
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