How to migrate DHCP server?

[Cooky]

We're retiring our old domain controller, which has DHCP running.

What do I need to do so that the new DHCP server won't assign any IP's that are already assigned to clients so that there won't be any IP conflict?

I know in Windows server 2003 you can backup and restore DHCP database. Will that do it?


Edit:
MS has a special tool that does exactly what I want.

 

[Genx87]

Not sure but what do you mean more specifically?

I take it the new DHCP server will provide address's for the same range right? If so I have done it by shutting down the old DHCP service and creating a scope on the new server. Provided nobody is trying to grab an IP addy during the 5 minutes you are doing this, all should be ok.

 

[Cooky]

Yes we'll use the same scope / IP range on the new DHCP server.

Say the range is 10.10.1.1 - 10.10.1.10, and someone already has 10.10.1.1 from the old server.

When I turn on the new DHCP server, will it be smart enough to know that a client host already has 10.10.1.1 and therefore will start serving from 10.10.1.2, or whatever IP that's not already assigned by the old server??

In another word, when I turn on the new server, will the lease table contain the leases from the old server if I do a DHCP restore?

 

[Genx87]

Originally posted by: Cooky
Yes we'll use the same scope / IP range on the new DHCP server.

Say the range is 10.10.1.1 - 10.10.1.10, and someone already has 10.10.1.1 from the old server.

When I turn on the new DHCP server, will it be smart enough to know that a client host already has 10.10.1.1 and therefore will start serving from 10.10.1.2, or whatever IP that's not already assigned by the old server??

In another word, when I turn on the new server, will the lease table contain the leases from the old server if I do a DHCP restore?

Tis a good question but I think Windows machines will note a duplicate IP on the same network if it happens and seek out a new IP from an available dhcp server.

One thing you can do before you bring down the old DHCP server is release all the IPs. This should cause the clients to look for a new IP when you bring up the new DHCP server.

 

[Cooky]

I came up w/ two solutions:
1. To migrate from Win 2000 server and before to Server 2003, MS has a special tool that moves the DHCP database from one server to another, and preserves the DHCP config and leases.
(this is what I used and it worked)

2. In the DHCP server properties, there's an option to check if there's duplicate address before assigning a client IP. This I assume won't work well cause if you have a large network, the server will have to check so many IPs that you might get a timeout.

 

[JRock]

Link to tool?

 

[Cooky]

Link
This is the link to the page that explains how to do it. The link to the tool is on that page.

 

[JRock]

Originally posted by: Cooky
Link
This is the link to the page that explains how to do it. The link to the tool is on that page.

:thumbsup:

 

[randal]

I know that ISC's dhcpd attempts to ping the IP address that it is about to lease to a client - if it receives a response, it tries another IP from the pool. I do not know if MS DHCP does this, though.

 

[Garion]

Man, that's the hard way.

Easy way:

A week or so before you move, you turn down the DHCP lease times to ~4 hours. A day before you move, turn them down to 15 mins.

Turn off the old one, turn on the new one with a 15 minute timer and voila! 15 mins later all problems are resolved and everyone gets a new IP. Give it a day or two then set the lease times back up where they were before.

- G

 

[Cooky]

and you couldn't have told me this before I went through what you called the "hard way"?
just kidding.
We thought about changing the lease time, but then we felt it would be a pain to manually set up all the DHCP reservation and scope. Microsoft's mover tool saves us a lot of hassle.
Everything's moved over w/ that tool.

 

[nweaver]

I hate MS DHCP as there is no import method, except from an export. We had ~750 PC's to put into several pools on one DHCP server, we had the IP to Mac with Computername in CSV from another tool (these were all static set, what a pain). I finally used perl to parse the csv file and put it into a text file as a netsh script.