Project Plan to change subnet mask

I am evaluating a change in the subnet mask on my networks.  I have an all Windows Server 2012 R2 server domain network.  Clients obtain their IP addresses via DHCP.  Servers and other devices have static IP addresses.  I have one point to point VPN that connects a remote office to the domain.  Please provide references to documentation that could provide the basis for a project plan to accomplish this migration.
BeurmannPrincipalAsked:
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bbaoIT ConsultantCommented:
better to know more details about the existing and projected IP plans. e.g. DHCP scope and its subnet mask, servers' IP scope with their existing and projected masks.

if the situation meet some criteria, you may work out a smooth plan to deploy the new mask in steps while keeping all servers accessible to the client computers.
BeurmannPrincipalAuthor Commented:
Hi,
The existing network has the standard subnet mask:  255.255.255.0.  DHCP scope is 101 to 200.  The static IP range of the servers and ancillary equipment is 002 to 100.  The IP address range is 192.168.0.0/24.  The IP address of the remote office that is 192.168.1.0/24.
Mike Beurmann
bbaoIT ConsultantCommented:
what about the new mask?
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nociSoftware EngineerCommented:
Now if you want to grow you network by doubling, Lets assume this because of lack of info in the Question,
netmask from /24 -> /23 (255.255.255.0 -> 255.255.254.0)
For a transistion it is needed to know 2 of the next 3 things..... (Starting situation, Ending situation, Difference between start & end).....
Ok work break down....

Doubling the range means... the base range of 192.168.0.0/24 will become 192.168.0/23  it will also invade 192.168.1.0...
Therefore you will need to move the remote network from the address range 192.168.1.0/24 to something else (192.168.9.0) or beyond. Moved to *.9.0 or higher so you can do this doubling trick again.
So that is the first task.  This can be done cold turkey or by using alias addresses as in between on the remote site.
and moving systems one by one.  and finaly remove all 192.168.1.0/24 reference on remote.

After that you can on a quiet moment adjust all netmasks on the main site. (DHCP by adjusting the netmask provided and all static configs by hand/script etc. Dont forget to also update the remote router if needed.

Now you have to take inventory and determine the time all tasks consume and start making a planning.
And define intermediate stable states you can leave your network in if the planning is not met in time.
Also make a plan how to undo parts of changed to ge back to a previous stable state. and the time it takes.
Determine the windows of opportunity the network is quiet.  
During many of the steps in  the change the network will NOT be stable prepare for that.

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BeurmannPrincipalAuthor Commented:
I hadn't selected the new subnet mask, as I had anticipated that I would include its selection in the planning, much as noci indicates.
BeurmannPrincipalAuthor Commented:
Thanks NOCI.
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