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New Member

Access Points Not Passing DHCP to Clients

I have a 50+ access point deployment, all in a single VLAN (DMZ), across a dozen buildings. We recently experienced wierdness of the following sort. Clients would request DHCP request, DHCP servers would forward requests, which would not get passed from the AP to the clients. We could verify that DHCP and all other parts of network were fine. I had to cold boot each AP to clear the condition. I could find nothing in this mix of 350s and 1200s or the spectrum that would indicate an obvious attack... Couldn't find where to start looking for any tables that were full, or any real place to look for some other reason for this. Yet after cold boot- all is well.

Any thoughts, in case it happens again?

9 REPLIES
Silver

Re: Access Points Not Passing DHCP to Clients

You might want to try giving your equipment a firmware upgrade.

New Member

Re: Access Points Not Passing DHCP to Clients

I have seen something similar at our site but the user would have to reboot his system several times before getting in. We tried to release/renew but that would never work only reboot. We are still working this issues but it looks like the user is never authenticating so an IP will not be received.

Have you found anything yet?

Thanks

New Member

Re: Access Points Not Passing DHCP to Clients

I had the exact same problem but the clients were Symbol hand scanners. Cisco 350 Aironet cards worked OK. It was the Symbol client SW rev.

New Member

Re: Access Points Not Passing DHCP to Clients

I was having a similar problem where a laptop would get an address but an iPaq handheld wouldn't.

I finally got it working by going to the interface page on th IOS web setup and under DATA RATES leaving REQUIRE for 1 and 2 Mb/sec and changing 5.5 and 11 Mb/sec to ENABLE. This effects the rate of broadcasts

Seems that the iPaq doesn't like broadcast communication faster that 2.0Mb/sec, and that was affecting DHCP.

New Member

Re: Access Points Not Passing DHCP to Clients

OK, I think I have an answer to some of the problems here. The iPaq DHCP implementation is flawed and that goes for the Symbol device too most likely (PPC2002). The problem is, the iPaq will send out a request and not see the reply. The only real solution I've found is a soft reset(it's practically how I turn it on now). It doesn't always do it, but it does it often enough to cause problems. Pocket PC networking is just buggy IMO and needs some serous work.

mhs
New Member

Re: Access Points Not Passing DHCP to Clients

I am having this exact same problem on 12.2.13JA2. AP 1200 works fine for DHCP initially after a fresh reboot. THen at some point stops broadcasting DHCP requests. When the AP is rebooted the probkem is rectified. Have not gone to 12.2.15 yet as we had problems loading this OS. Was the data rate change the correction to this problem?

Thanks

Paul

New Member

Re: Access Points Not Passing DHCP to Clients

Hi Guys,

I am having a similar problem to you, however i can get authentciated via LEAP, but dont seem to get an IP adderss from the radius server.

My setup is very simple as i am at the design stage. We have a Cisco AP 1200 (2.4 and 5.0 GHZ) and we are using FUNK steel belted RADIUS server. LEAP authentication works fine and i can see the association on the AP. The wirless client (HP W400 integrated Wireless cards) shows that it has been authenticated successfully too. However no IP is being received. We have a IP Pool configured on the SBR server and the SBR server shows that it has issued an IP address.

Next step was to place a sniffer and capture the packets. The capture shows the radius requests and challenges and in the very last ACCEPT packet we can see that the SBR has issued an IP address.

I am confused as i cant see anything on AP that would block the IP address. There are also a few attributes showing as "unknown" in the sniffer trace, so im not too sure wgats going on.

Can anyone help. The IOS is 12.2 (13) JA

New Member

Re: Access Points Not Passing DHCP to Clients

Do this

AP# conf t

AP#(config)IP DHCP-SERVER ?.?.?.?

Save and give it a try.

Robert

New Member

Re: Access Points Not Passing DHCP to Clients

Hi all... I dont have an answer for this, but if u tried working with no encryption all ur clients will obtain IP from the dhcp server!

seems to me as incompatibility between the network adaptors and the AP... also u may remove the adaptors key and put it again this work most of the time! or disable the adaptor and re enable it again..

Good Luck!

Hani Farouk

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