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I have a server, DHCP1 running on Windows Server 2008 and I want to migrate it to Windows Server 2016 without downtime to the DHCP service.

My problem is that I have to maintain the same hostnames and IP Addresses for the 2016 server. So I’ll have to bring down the 2008 server, replace it with a 2016 server and import all the configuration I exported from the 2008 server.

During this migration, how does my client knows which server they are going to connect? On what basis, my client will determine whether it has connected to the Windows 2008 server or Windows 2016 server since both servers has the same IP address and same hostname.

Selvakumar
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1 Answers1

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Migrate to a new name and IP to reduce conflicts and confusion. Also, reverting the change if necessary will be easier if the old one is still on the network.

DHCP will discover the new DHCP server, that's what it is designed for. From a Windows role migration guide, emphasis mine:

DHCP Server clients that attempt to renew an IP address lease send the renew request to the previous IP address of the DHCP server. If the source server has been decommissioned and then disconnected from the network and the new DHCP destination server is operating with a different IP address, this request initially fails because of the changed IP address. However, clients try to rediscover the IP address of the DHCP server on the network and therefore recover from this transient failure.

Regarding no downtime, tricky. A short downtime is required in between exporting and importing DHCP. Clients keep their leases, so this only impacts renews and new devices for a couple minutes. Running multiple independent DHCP servers on the same subnet risks conflicting addresses. The complexity is not worth chasing a few seconds of uptime, any problems will be limited and temporary.

John Mahowald
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