I'm planning a migration of around 55 virtual machines from one datacenter to another, and it will likely involve changing their IP addresses. These VMs don't handle DNS, DHCP, or any domain controllers, so I'm aware of the interdependencies involved. My main question is whether the migration process simply involves applying the new IPs, updating DNS records, flushing DNS on the necessary servers, and ensuring everything resolves correctly. We're not using any applications or processes that directly access these VMs by IP—just want to make sure I'm not missing anything important!
3 Answers
Ensure all your systems resolve other hosts by DNS names, and plan to update DNS entries as the VMs are being migrated. If none of your applications have hardcoded old IPs, you should be fine. It’s worth checking your configuration files and local hosts files for any hardcoded addresses. Also, be aware that some applications might rely on MAC addresses for licensing, so those could be affected too. Good luck with the migration!
Make sure your DNS zones are correctly configured on your servers. Also, verify that any services running on your servers can handle IP changes. We had an issue where a self-hosted application didn’t react well to an IP change; it required some manual edits in SQL and tweaking certain configuration files. Most clients connected via hostname, but the server software really struggled with the switch—so watch out for that!
Yeah, this migration will definitely be a slow and steady process. It's smart to go system by system, starting with non-production environments first.
If you're moving to a new datacenter, is there a reason you can't keep the same IP range? Do you have a site-to-site link set up for the new location?
I’m not sure yet, just trying to prepare for all possibilities. I work at a University, and my current datacenter is shutting down. One VLAN is non-routable without purchasing extra hardware, which isn’t in the budget, so I might have to get the servers onto a managed VLAN instead.
You can actually extend a subnet to multiple physical locations. We're in the process of moving our datacenter to Azure VMware Services with a consultant's help.
Thanks! I've seen many pitfalls, but a few always sneak by. I have one system that might be affected, but luckily, I have a test environment and a solid rollback plan—my setup is pretty small!