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  • Increase network mask

    hi.

    Would you please tell me the steps how tochange network mask in 3 DC in replication.

    From mask 255.255.254.0 to 255.255.248.0.

    Is okay if I do (change) first DHCP scope dump to .txt, then change and import back to dhcp server, then this repeat to all of DC. But what else must I do, to change a network mask in correct sequence, that this all three domain controlers will work like now.

    Thank you for help, and sorry for my english.

    BR.

  • #2
    Re: Increase network mask

    As long as the netmask values are the same on the NICs of all 3 DCs, they should talk to each other without issue. DHCP has nothing to do with that. But you can't simply decide to extend the mask on it's own, the network number has to be correct for your new addressing scheme to work. What is the current network?

    As for DHCP, assuming you're talking about Microsoft's DHCP: you can change the network mask, but only be deleting and then re-creating the desired scope with the new mask. While their GUI will let you change things on-screen, the service won't pick up the changes and your address space won't increase.

    Again, to be better advised, we'd like to know what your current network range is to let you know whether it can be extended as-is, or if something else may be needed.
    *RicklesP*
    MSCA (2003/XP), Security+, CCNA

    ** Remember: credit where credit is due, and reputation points as appropriate **

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    • #3
      Re: Increase network mask

      Like Rickles says, there's a lot of considerations when changing the netmask. All devices with static IPs will need to be changed. Routes will need to be updated. And no conflicts with existing subnets needs to be ensured.

      In my experience, changing the netmask on the DHCP server, if the scope is local, will cause it to hand out IPs with the configured netmask.

      But why are you changing your mask to /21? Are you really going to have 2046 devices on the same network? Or are devices going to have multiple IPs?
      Regards,
      Jeremy

      Network Consultant/Engineer
      Baltimore - Washington area and beyond
      www.gma-cpa.com

      Comment


      • #4
        Re: Increase network mask

        Originally posted by fireflymaster View Post
        hi.

        Would you please tell me the steps how tochange network mask in 3 DC in replication.

        From mask 255.255.254.0 to 255.255.248.0.

        Is okay if I do (change) first DHCP scope dump to .txt, then change and import back to dhcp server, then this repeat to all of DC. But what else must I do, to change a network mask in correct sequence, that this all three domain controlers will work like now.

        Thank you for help, and sorry for my english.

        BR.
        1. Hope you are not running DC with dynamic IP. Otherwise you are going to have lots of issues.

        2. If you have a spare IP range which I assume the 255.255.248.0 is, all you need is to configure it in the different DCs for them to communicate. If DNS services is running, make sure all clients and servers can communicate with the DNS server. (Changing the Server options under DHCP for 005/006 DNS Server should work, otherwise you will be in alot of pain)

        3. Ensure clients, servers and the DCs can communicate with each other. NSLookup and Ping.

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