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DHCP role migration

Hi,

Can anyone please share and assist me the steps by steps of how to migrate the DHCP settings and role from Server 2003 into the newly build domain controller running on Server 2012 R2 ?

Thanks,
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Distinguished Expert 2019

Commented:
You can have two DHCP in the environment while using exclusions to make sure the two do not offer/allocate the same dynamic IPs.
Netsh dhcp server dump will export the config which you can edit and import on the 2012 dealing with static reservations if any.

The process is fairly straight forward. Add the role to 2012. Authorize it. Add the scope with the exclusions of Ips being allocated by the 2003. If you do not have static reservations. Adjusting/configuring the scope options to allocate name servers, ........

Author

Commented:
ok, but the existing workstations who already got IP address won't be suddenly lose its IP right ?
Sr. Systems Administrator
Commented:
take a look at this article for steps on migration; it includes screenshots

Step-By-Step: Migration of DHCP from Windows Server 2003 to Windows Server 2012
http://blogs.technet.com/b/canitpro/archive/2013/04/29/step-by-step-migration-of-dhcp-from-windows-server-2003-to-windows-server-2012.aspx

the existing workstations who already got IP address won't be suddenly lose its IP right ?

clients that get DHCP addresses have a lease and it will keep that IP address until the lease expires
if you have yours configured for 2 days, the client will keep that IP address for 2 days before looking to renew it
it won't lose its address if the DHCP server is down during the lease period
Distinguished Expert 2019
Commented:
The workstations that have IPs will retain them for the duration of the dhcp lease time.  As the lease time approaches expiration, the workstation will initiate an IP renewal process. When the old DHCP server is no longer available or is busy and not responding, the new DHCP server will receive the request to renew the existing IP which will be denied and a new IP will be offered by the server and accepted by the workstation.
Certain appallications might not like the transition and alert the user, but some will be transparent.

First thing is to make sure to add an IP exclusion range on the old DHCP. To allow for both running on the network without leading to two systems being given the same IP. Time for the new restrictions to be in place should be allowed.

I.e. The current server handing out
Scope 192.168.0.2-254 netmask 255.255.255.0
Exclusion block for static/server use: 192.168.0.2-31
No reservations for this example.
First thing, you would carve out a block of IPs by adding another exclusion block: 192.168.0.200-254 (is is the block that the new server will allocate)

On the new server
Dhcp scope 192.168.0.2-254 netmask 255.255.255.0
Static exclusion block: 192.168.0.2-31
Original dhcp server exclusion block: 192.168.0.32-199 (server A exclusion)
In this setup SERVER A will allocate IPs from 192.168.0.32-199 while server B will be allocating IPs in the 192.168.0.250-254 block

When the current 2003 server is removed from the network, or it's DHCP server de authorized, remove the server A exclusion from server B.

The dhcp server have as part of the server properties a conflict detection option, I.e. Delay in response and it uses ping to determine whether the IP is in use, the addition of the windows firewall active by default often has the block on icmp (ping) defeating the check.

Author

Commented:
ok, so in this case I can just enable the role but not authorizing the DHCP yet.

Author

Commented:
Thanks !

Author

Commented:
do I need to reduce the DHCP leasing period one day before the cutover time from 5 days into 1 day to ensure the workstation can seamlessly cutover with no downtime ?
Distinguished Expert 2019

Commented:
if your lease period is 5 days, you need to make the change 5 days before the cutover.  to avoid the new server when it kicks in from allocating an IP that is in use.
Add the IP segment exclusion while reducing the lease time to 5 hours.
If all your DHCP clients are workstations that are shutdown at night, you can transition at a faster rate.
The workstations will discover the new DHCP server during their IP renewal process.