DHCP: Migrating a scope from Cisco Net Reg to Windows DHCP Server 2106 RRS feed

  • Question

  • Hi There

    We are currently preparing to migrate from Cicso CNR DHCP server to Windows DHCP server in our organisation.  Our organisation has approx 800+ scopes mostly which are mainly /24 subnets. For 

    My plan is too import all these scopes in using a script but I am manually adding the first few scopes.

    As a test I have set up a scope on the Windows that morrors the scope on CNR.

    My plan is to change the 2 IP-Helper addresses on the Vlan from the 2 CNR addresses to the 2 new Windows addresses.

    The problem is that within the scope I am using as a test ( there are only 30 available IP addresses. I am concerned that when I change the helper address there will be issues in that there is not a big enough available pool within that subnet to faciltate migrating to the new servers smoothly.

    Any advice and procedure suggestions would be much appreciated.



    Friday, June 22, 2018 11:19 AM

All replies

  • Hi,

    Thanks for your question.

    Please try the following suggestions to see if it could be of help.

    • Unless you go out and release/renew everything, you're going to have conflicts. The lease time won't force a client to change an IP it already has unless it goes to check its lease at startup or ipconfig /renew.

    When changing the DHCP server, using a different IP range is a feasible method. Then wait a while for everything to be rebooted (or till you can go release/renew everything), so there are no conflicts.

    • Another way is to set conflict detection for a while until you get cut over completely. You can use this procedure to specify how many times the DHCP server tests an IP address before leasing it to a client.


    Note: This increases the load on the server. A value of no greater than 2 for ping attempts is recommended.

    Refer to the following link:Enable IP Address Conflict Detection

    Hope you have a nice day!

    Best regards,


    Please remember to mark the replies as an answers if they help.
    If you have feedback for TechNet Subscriber Support, contact

    Monday, June 25, 2018 8:58 AM
  • Hi,

    Was your issue resolved?

    If you resolved it using our solution, please "mark it as answer" to help other community members find the helpful reply quickly.

    If you resolve it using your own solution, please share your experience and solution here. It will be very beneficial for other community members who have similar questions.

    If no, please reply and tell us the current situation in order to provide further help.

    Best Regards,


    Please remember to mark the replies as an answers if they help.
    If you have feedback for TechNet Subscriber Support, contact

    Thursday, June 28, 2018 6:58 AM