DHCP on laptops

[StewartKnight]

We have a loads of laptops, some Dells with built in wifi, and some others with wifi cards.

 

None of them pickup and ip address by DHCP. is anyone else having this problem, is everyone giving laptops static ip's?

[Dos_Box]

They won't pick up an IP address until they have logged onto the base station. So if the user has not entred the WEP or other encryption key then an IP address will not be issued. Aslo, have you entred all of the correct network details into the base station and disabled the base stations own DCHP server?

[StewartKnight]

I understand why the little blighter aren't getting the ip address, I just wondered if anyone else had the problem, and what they did about it!

[OverWorked]

Stewart,

 

Glad to know I'm not alone. I've had the same problem for about a year. Most of my access points have no problem. A few have this persistant problem where they get a good signal strength but cannot get DHCP.

 

Giving them a static IP works (temporarily, and only sometimes) but this is not the ideal solution.

 

Resetting the AP (switch off and on) usually fixes it for a few hours, then the problem comes back.

 

Sometimes resetting the AP and giving them a static IP doesn't work at all. This is the most frustrating.

 

The AP's that have this problem are connected to a 3com managed switch, so this seems to be the common cause. Other APs connected to cheap unmanaged switches work for weeks on end no problem.

 

Elus1v said that he had the same problem and fixed it by turning off spanning tree protocol on the ports the APs are connected to. I'm only vaguely aware of what STP is. I'm still looking into it and will let you know how I get on. I'll have a proper look next week when the school's closed.

 

Please let me know if you find a fix. I've googled for dhcp, "cannot connect", wireless, but not found anything useful - just sites selling wireless gear.

 

I don't think it's anything to do with security, as our wifi doesn't have any! (I shouldn't have said that publicly)

[StewartKnight]

no, I don't have any security here, but the walls are thicker than the teachers, and there are no houses nearby anyway!

[woody]

I think this could be something to do with the route from the access point through to the DHCP server. We found that we could plug an access point to the network through one particular switch, and all connecting laptops would not get an ip issued. Then we plugged the AP into the switch which had the server connected directly in and there were no problems. I don't know exactly why this happened but I presume it was a routing issue.

 

Stewart, maybe you could try this. If that doesn't work, then you've stumped me!

[StewartKnight]

I think it must have something to do with global warming, everything does these days you know!

[OverWorked]

@Mark

 

That sounds about right. It's definitely something to do with the switches. I just need to know what exactly. It's some sort of configuration/protocol problem.

 

The trouble is I can't just replace the problem switch, as it handles the fibre link between the two ends of the school.

[GrumbleDook]

Depending on the laptop there is a dell utility that once the machine has started up and someone attempts to log on it will check that it can connect to the WLAN, has a valid IP Address, the DNS servers are contactable and then will authenticate.

 

I believe it is imaginitively called the Dell Wireless Utility.

[OverWorked]

I've tried the utilities that come with the wifi cards. I have various makes, but not Dell.

 

They're all useful for giving the MAC addresses of the APs it can find, and the signal strengths, but they still can't do anything for the DHCP.

 

If I click 'repair' for the connection, it all goes well, until it tries to get the IP address. It tries for about a minute, then gives up. ipconfig /renew is the same.

 

At this point I can set a static IP and it works, then set it back to dhcp and it won't.

 

What's bizarre is that this problem only affects wireless, not wired. If I get a patch lead and plug the laptop into the wall, there's no problem. This eliminates the DHCP server as the problem.

[StewartKnight]

here the problem though, the kids can't log on until the laptop has an ip, and only when you're logged on, can you mess with the wireless connection!!

 

 

ARRGGGG!!!!!!

[GrumbleDook]

The Dell Util solves that by forcing it to check it has a valid connection, a valid IP address (or if not it runs "repair") and check it can talk to the DNS servers (and so hopefully the DC) before trying to authenticate.

 

This does not stop the administrator logging onto a local account though ... just in case things go even worse.

[OverWorked]

Same here. Can't log on to the domain.

 

I have to log on as local admin, and try to repair it. Sometimes it works, sometimes it just won't.

[jonny_valentine]

I had same prob in several schools, heres what i did:

 

remove all network card utilites, install xp sp2.. let windows manage the wireless, and all should be fixed, you may find you will have to login a couple of times to get it to keep the wep key there, make sure the blox that says, 'the key is provided for me' is unticked.

[OverWorked]

That's what I did first. The machines all had XP SP2 and were using windows, not the vendor's utility to manage the connection.

 

You're right about the vendor's utilities, though. I have many problems with these, and always find the windows management is much better.

 

I'm confident that I've fixed it now, thanks to E1uSiv3.

 

In my case it was the fancy 3com managed switches that were causing the problem. I disabled Spanning Tree Protocol on the ports that the AP's connect to. (Once I'd worked out how to do this).

 

I did this at the start of the holidays, then left it. I've just checked them again this morning (first day back), and they all work. Hooray! I've had this problem for about a year, and now think I've finally solved it.

[E1uSiV3]

woohoo nice to know i come in useful from time to time lol