Wireless Networking - DHCP problems

[Guest]

We have a network of xp pro -sp2 clients and 2003 servers. Some of these are
laptops which connect to our network wirelessly, and these are giving us
problems. As far as I can tell they are not reliably getting DHCP information
from the server, and so self-allocate an IP which is not on our network.
Packet-sniffing suggests that the issue is not the DHCP request going to the
server, but the answer packet returning to the laptop.
Turning off encryption on the AP makes it significantly better, but does not
completely fix the problem.
Things appear very slightly better if I use WAP as opposed to WEP
We do not have a big enough IP space to allow all our APs to provide a a
DHCP range themselves (which I had considered as a solution!).
We have the same issue on both 3com and a NetGear AP - though two of our APs
work very consistently.
I've put a laptop directly adjacent to the AP, so I can rule out the
building structure I think.

I think I can identify the issue as being DHCP related as when I give the
laptop a fixed IP address there is no issue, but I'm unsure how to rectify
this problem. I'm unwilling to leave the ap unsecured for obvious reasons

 

[Steve Winograd [MVP]]

We have a network of xp pro -sp2 clients and 2003 servers. Some of these are
laptops which connect to our network wirelessly, and these are giving us
problems. As far as I can tell they are not reliably getting DHCP information
from the server, and so self-allocate an IP which is not on our network.
Packet-sniffing suggests that the issue is not the DHCP request going to the
server, but the answer packet returning to the laptop.
Turning off encryption on the AP makes it significantly better, but does not
completely fix the problem.
Things appear very slightly better if I use WAP as opposed to WEP
We do not have a big enough IP space to allow all our APs to provide a a
DHCP range themselves (which I had considered as a solution!).
We have the same issue on both 3com and a NetGear AP - though two of our APs
work very consistently.
I've put a laptop directly adjacent to the AP, so I can rule out the
building structure I think.

I think I can identify the issue as being DHCP related as when I give the
laptop a fixed IP address there is no issue, but I'm unsure how to rectify
this problem. I'm unwilling to leave the ap unsecured for obvious reasons

Are the problem computers getting addresses in the 169.254.x.x
"Automatic Private IP Address" range? If so, it means that they can't
communicate with a DHCP server. The problem could be with the
wireless access point -- I've seen cases where an access point doesn't
properly pass along DHCP traffic.

Are the problem computers getting addresses in any range other than
169.254.x.x? If so, there could be a rogue DHCP server on the
network. In that case, what do the computers show for their DHCP
server address? Does that address respond if you ping it?
--
Best Wishes,
Steve Winograd, MS-MVP (Windows Networking)

Please post any reply as a follow-up message in the news group
for everyone to see. I'm sorry, but I don't answer questions
addressed directly to me in E-mail or news groups.

Microsoft Most Valuable Professional Program
http://mvp.support.microsoft.com

 

[Guest]

Thanks for replying Steve

Yes, it's the automatic IP, which is what tipped me off to the fact that
they're not making successful DHCP calls - it does seem to be the answer
packet not coming back rather than the request packet not making the server.
Any ideas what causes it?

andi