Disabling old scope.. creating new one (2003 DHCP).. clients affected?

[markm75]

I cant recall the answer to this one:

what happens if i disable a scope and create a new scope.. any machines with ip addresses already? will they auto reconnect and get a new one when the new scope is active or will they need to be shutdown then restarted?

I have one user worried they wont be able to remote desktop via vpn to their machine after i make this change tonight (without first shutting off the machine and restarting it).

Anyone know/recall what will happen in this event.

(My original scope range will be changed, after i disable the old scope, then creating the new one).

Thanks for any responses...

 

[lhuegele]

Is your subnet changing or will that remain the same? If your subnet is also changing with this new scope, you may have to do a /release and /renew on all machines so they can get the new scope.

Just open a command prompt and type the following commands:

ipconfig /release
ipconfig /renew

Then do an "ipconfig /all" to make sure they have the new IP information.

Good luck,

 

[markm75]

The subnet will stay the same..

Just the range of dynamically allocated ips will be different..

ie: old one .10 to .250.. (split 50/50 over two servers) new.. .10 to .225 (split 80/20) over two servers

 

[markm75]

I made the changes last nite.. so here is the real answer from experience..

Once you disable and remove the old scope, create the new one..

All existing ip addresses will remain active until they try to get a new lease.

This causes issues as if some machines dont reboot right away, you'll try browsing to them and get the wrong machine due to the dns mismatch.

So in short,

After changing dhcp it is best to either have your users reboot or open a command prompt and do the ipconfig /release then ipconfig /renew.

Once all machines have done this, there wont be any ip conflicts or dns issues.

 

[lhuegele]

I think you're going to have to force the /renew. We did that here when we changed DHCP servers. We used our log-in script to force the IP renew.

Good luck,

 

[ShackDaddy]

In my experience, the best way to do this is:

1) reduce the lease time down to 6 hours--do this a week before your DHCP migration.

2) disable to the one scope and enable the other. Clients renew their leases every time half their lease is up. By the time 3 hours is up, every workstation with a lease that is powered on will have tried to renew their lease, gotten a NACK from the server that forced it to drop its current address, and will have retrieved an address from the new scope.

3) Once your migration is complete, go ahead and reset the lease time to a more standard length of time, often 8 days.

Using this strategy you'll compress the actual migration process down to 3 hours, and won't have to /release /renew anywhere.

ShackDaddy
Shackelford Consulting