Laptops moving between subnets retain old subnets addressing

[HacksNTweaks]

OK, here's the scenario:

W2K server running DHCP server and dynamic DNS (no WINS). There are 4 scopes within a superscope set up as follows:
10.2.x.x/16 (10.2.1.1 - 10.2.2.254)
10.3.x.x/16 (10.3.1.1 - 10.3.2.254)
10.4.x.x/16 (you get the idea!)
10.5.x.x/16 ("" "&quot
The subnets are "routed" using a Cisco layer 3 gigabit switch using IP helper address on each appropriate interface.

The clients are either W2K or XP. They pick up appropriate IP configuration information on their respective subnets and all is fine and dandy the first time they are ever booted up on the network. Pretty straight forward stuff, but...

The problem:
A good number of users (laptops) must move between subnets (carried on separate VLANs). What's happening is that they retain their PREVIOUS subnets dynamic IP addressing information, thus can't log on to the domain. I've tried having them do a release before shutdown to no avail. The only thing that works is to delete the DHCP lease entry for that IP address in the scope. Then, they can pick up an address for the correct subnet after a reboot. This has also happened with a DHCP configured Intel print server (don't ask the obvious question here. It has to do with the previous admin!).

Is there some setting I'm missing here, folks!? Like on the layer three switch config, or the DHCP server config?

Any help is truly appreciated!

HacksNTweaks

There are 10 types of people in the world. Those who understand binary, and those who don't.

 

[GlenJohnson]

Create an advanced user class in dhcp, add all the laptops that are having the problem to this and give them a very short ip duration so they will have to get a new ip address from dhcp more often. This should solve your problem. Good luck.

Glen A. Johnson
Johnson Computer Consulting

http://www.johnsoncomputers.us

"The best fire does not flare up the soonest."
George Eliot (1819-1880); Englist novelist.

Want to get great answers to your Tek-Tips questions? Have a look at FAQ219-2884

 

[HacksNTweaks]

Thanks, Glen, for your response.

I should have clarified. This is a teaching environment. Thus, unfortunately, it could be any laptop (lotsa laptops)! Usually only a handful of users (tech users, so to speak).

What I don't get is that the server should issue a DHCPNak when the doggone thing recognizes that the client, requesting his old IP (via it's MAC value), is on a different subnet.

Per Microsoft:
The Requesting State

If the IP address of the client was known (that is, the computer restarted and is trying to lease its previous address), the broadcast is looked at by all of the DHCP servers. The DHCP server that can lease the requested IP address responds with either a successful acknowledgment (DHCPAck) or an unsuccessful acknowledgment (DHCPNak). The DHCPNak message occurs when the IP address requested is not available or the client has been physically moved to a different subnet that requires a different IP address. After receiving a DHCPNak message, the client returns to the Initializing state and begins the lease process again.

Could it have anything to do with the fact that the subnets are riding on VLAN's. This was just implemented. I don't think that's it, but...?

HacksNTweaks

There are 10 types of people in the world. Those who understand binary, and those who don't.

 

[GlenJohnson]

Could it have anything to do with the fact that the subnets are riding on VLAN's. This was just implemented. I don't think that's it, but...?
How long has the problme been going on?

Glen A. Johnson
Johnson Computer Consulting

http://www.johnsoncomputers.us

"The best fire does not flare up the soonest."
George Eliot (1819-1880); Englist novelist.

Want to get great answers to your Tek-Tips questions? Have a look at FAQ219-2884

 

[bradsm]

Hi there,

I had this exact same problem and it had me stumped for a while.

I've read documentation that advises a SuperScope is just a usefull way of grouping your scopes together and actually has no effect on how your scopes function.

This is not true, as all your scopes are a member of one Superscope the Superscope allows the DHCP Server to provide leases from more than one scope to clients on a single physical network.

You can use a Superscope to group scopes together that serve subnets on the same VLAN only.

In other words, if you delete the Superscope and just have the scopes it will fix your problem.

Hope this helps,

Matt