Two domain controllers on same subnet

Question

Will it cause an issue if I have two domain controllers on the same subnet? I'm wanting to migrate my current domain controllers to new hardware and I'm wondering if I can just stand up another domain controller locally and then decommission the old domain controller. Would this cause any issues? Domain controllers are not doing DHCP.

Answer 1

No issues, in fact that's the simplest method of migration.

The two prerequisites to introducing the first 2019 domain controller are that domain functional level needs to be 2008 or higher and older sysvol FRS replication needs to have been migrated to DFSR
https://techcommunity.microsoft.com/t5/Storage-at-Microsoft/Streamlined-Migration-of-FRS-to-DFSR-SYSVOL/ba-p/425405

I'd use dcdiag / repadmin tools to verify health correcting all errors found before starting any operations. Then stand up the new 2019, patch it fully, license it, join existing domain, add active directory domain services, promote it also making it a GC (recommended), transfer FSMO roles over (optional), transfer pdc emulator role (optional), use dcdiag / repadmin tools to again verify health, when all is good you can decommission / demote old one.

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