Best Practice for changing TCP/IP

Posted on 2005-04-07
Last Modified: 2010-04-18

All, we will be changing our IP from 128.x.x.x/16 to 192.168.x.x/16 this weekend. As of now our firewall is the dhcp server and we plan on decommisioning that service and setting up a windows server 2003 to be the dhcp manager. In what order should I be making this change so I don't lock myself out of any switches or routers during the process? BTW we have a flat single network of 80 users and 12 servers.

My plan is as follows:
1) Stop DHCP service on firewall
2) Change internal LAN connection to
3) Change IP on DHCP server to 192.168.X.X
4) Authorize DHCP server and active scope []
5) Change IP on switches
6) Manually change all servers to 192.168.x.x
7) Recreate my one to one NAT on firewall
8) remove static IP's on desktops and create reservations

Question by:SANG501
    LVL 33

    Expert Comment

    Looks good

    9) ipconfig /renew on all workstations so that they get a new IP address from new DHCP servers...

    LVL 14

    Expert Comment

    As a backup, you can assign two static IP addresses to the NIC in the workstation you use, so that you can get to IP devices on both subnets at the same time.
    LVL 95

    Accepted Solution

    Rather than NJComp's suggestion, you could just set the lease time on the current DHCP server to 10 minutes.  Then when you shut it down the clients will try to renew within 5 minutes - saves you time of going to all the machines.  (Or use a time other than 10 - 20, 30, maybe even an hour).  Remember how DHCP works, halfway throught the lease it will renew itself.  I wouldn't recommend this be set that low NORMALLY, in part because of server load and network flooding of DHCP requests, but for a short time, things should be ok and you can then set the new server's lease time longer.
    LVL 1

    Author Comment


    Thanks for the valuable feedback. I am aware of the /renew for workstations and doing either of the two methods is fine with me. However, on the domain controller side of things, I would also have to change the push/pull partners IP for WINS, delete non-dynamic DNS entries and recreate them with the new IP, is there anything else I need? We have two domain controllers running Active Directory. Thanks.

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