How to synchronize dhcp statics / reservations between two domain controllers?

Posted on 2006-04-11
Last Modified: 2012-05-05
Hello all,

I have two windows 2003 server (both domain controllers, dhcp, and dns).  I know that it sychronizes and replicates dhcp by itself, but is there a way to auto-sync static IP addresses that you manually enter into the reservations so that both servers always have the same information?  For example, if I goto server1 and manually reserve an IP address, how do I make server2 also recieve that information without me having to do it?

Question by:mainemonty
    LVL 23

    Expert Comment

    Setting reservations only applies to that particular scope.

    It's best practice to create separate scopes on each DHCP server, with different IP assignments, that way there isn't conflicts or bad information.

    I'm actually unaware that DHCP servers in Windows sync their data between them...if so that's news to me.  I've always been under the impression that you created scopes on each server with different IP ranges simply because it doesn't replicate.


    Author Comment

    You are right Mr. Cleaner.  DHCP servers don't sync data, I misworded that and meant to say that wanted it to do so.  I am actually setting up 2 separate scopes on each DHCP server, but I'm just worried about all the static IPs that I reserve.  I need for a single exact copy of just the statics to exist between the 2 scopes.  I just wasn't sure if this was possible.  Basically if server1 (scope 0-100) goes down, I would still like for clientA (reserved IP of .50) to somehow maintain it's IP and connectivity, even though server2 has a scope of 101-200.  Maybe I'm just stretching, but just thought that I'd pose the question.


    LVL 23

    Accepted Solution

    After 50% of the lease time has passed, the client will attempt to renew the lease with the original DHCP server that it obtained the lease from using a DHCPREQUEST message. Any time the client boots and the lease is 50% or more passed, the client will attempt to renew the lease. At 87.5% of the lease completion, the client will attempt to contact any DHCP server for a new lease. If the lease expires, the client will send a request as in the initial boot when the client had no IP address. If this fails, the client TCP/IP stack will cease functioning.

    If you are really concerned about it, then you can create a separate scope on DHCP server #2 for the EXACT same scope and reservations as server #1 and leave it disabled/not started.

    Then if server #1 does go down for some reason for any extended period of time, you just start the "reservations scope" on server #2.

    Everyone else that was getting a normal DHCP lease on server1 will eventually end their lease and get a new IP from server #2 in the 101-200 range.

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