DHCP settings not always updating on XP Pro client

[rodda]

I have this problem on several laptops where a staff member uses their company laptop at home. The home router (Linksys or other) issues an IP via DHCP to the users company laptop such as:

IP:192.168.1.13
Subnet Mask: 255.255.255.0
Gateway: 192.168.1.1
DNS: 209.159.192.7, 209.159.192.6 (ISP DNS servers)

Then, the staff member comes into the company offices, connects automatically to our WLAN, and because we use the same subnet (192.168.1.x), it fails receive a new DHCP lease with the appropriate settings. If I vary the NIC off/on as administrator, a new lease with the correct settings are issued. We don't have any issues with DHCP otherwise.

The DHCP server is a Sonicwall Pro 4060 (which is way over-sized for our environment). Users do not have local administrator privileges. Not sure if this is a consistent problem or not...still investigating.

I'm not quite sure how to fix this?

 

[MadKing]

"Then, the staff member comes into the company offices, connects automatically to our WLAN, and because we use the same subnet (192.168.1.x)"

That why compagny use different subnet or network. Use a class A, class B or noit use 0,1,2 in the 192.168.x.x .

Also you can probably modify your gpo to let's ipconfig command allowed by your user.

 

[rodda]

I agree about the subnet, but we have 5 office locations, 170+ employees, 20 servers, 8 T1 routers, 40+ printers, workstations, thin clients, etc...so it would be a PITA to change our network class...at least for now, but I am going to plan for that in the future (class C was already in place when I began working here).

The GPO is a good idea, if not a bit cryptic for users...I'll look into that as a short term fix.

The interesting thing to me is this; if a user has the IP 192.168.1.12, and another device on the company network already has that static address because it falls outside of the company DHCP scope, the Windows DHCP client on the laptop apparently does not communicate it's existing IP (the 192.168.1.12) or any scope details with the company DHCP server (or vice-versa). Otherwise, it would realize it's IP is outside of the existing DHCP scope and request a new lease.

Looks like I need to research DHCP details a bit more...

 

[MadKing]

You can control on your side the DHCP lease time to make it shorter ( mosty for wireless clients). that will force to renew the address more often.

"The interesting thing to me is this; if a user has the IP 192.168.1.12, and another device on the company network already has that static address because it falls outside of the company DHCP scope, the Windows DHCP client on the laptop apparently does not communicate it's existing IP (the 192.168.1.12) or any scope details with the company DHCP server (or vice-versa). Otherwise, it would realize it's IP is outside of the existing DHCP scope and request a new lease. "

The dhcp server only give an address if someone ask him. It's will neither revoke an adress if two people use them. That happen when someone assing a static ip adress in the same dhcp range on is own. For exemple a laptop that as been in hibernate and doesn't wake up correctly. Check with those people that have the problem if the close the computer or use hibernate.

 

[rodda]

Hibernate is disabled (due to an incompatible application), but I'm quite sure the laptop is in standby with the lid closed when they bring it into the company offices. Since the laptop already has a DHCP lease from home within the same subnet, it doesn't request a new DHCP lease until the existing one expires.

Beyond allowing ipconfig commands, I don't believe there is an easy fix. The best solution would be a different subnet at the company offices. I'm surprised other small companies don't experience similar issues.

Thanks for your help...

 

[thiggins]

Can't you just have the user run a repair on the wireless connection?

 

[BriComp]

Could you not run a batch file upon system startup with the following it it?

IPCONFIG /RELEASE
IPCONFIG /RENEW

I suggest you also put something in the batch file to update a log file. Then it can be inspected to see when/if the batch file ran.