Wireless Clients unable to take IP Address

[Faisal Shabbir]

Hello friends,

I have an issue regarding wireless clients, these clients are unable to get IP address from DHCP. its been happening with a specific WLAN on specific location, when you moved from other location to affected location and try to renew the IP address its not renewing.

however if you give static IP address of affaexcted WLAN range ist working fine.

Please Advice ...!!!!!!!!!

Thanks and Regards,

Faysal

[Faisal Shabbir]

rest of the WLANS are working and getting proper IP addresses from affected location

[grabonlee]

Hi

More info is required. For example could you from the controller, debug one of the affected clients and paste the result. Also it would help to know what the wlan set up is and which equipment does the dhcp proxy, WLC or layer 3 switch.

Can you ping the dhcp server from either the WLC or layer 3 switch.

[Faisal Shabbir]

Thanks for your reply Osita, yeah i have four WLAN controllers on 6509 (two each), rest of the wireless vlans are working fine on the controllers,

Thanks

[Faisal Shabbir]

even the affected vlan is fine but there is one building where clients are not able to get IP address from DHCP server,

all Aps installed on that locations distributed over all four controllers.

[grabonlee]

Hi

Irrespective of the fact that the other wireless vlans are working, you still have a problem with one, and you need to provide more info so that we can help troubleshoot your problem. Each wireless vlan specified is it's own L3 subnet. So if you have different dynamic interfaces for different wlans, that doesn't mean they will all function, as a problem on one doesn't affect the rest. Hence the need for you to supply more info such as if you are using HREAP/Flexconnect or Local in addition to the info I requested above. Thanks

[Faisal Shabbir]

Hi ,

the affected WLAN is only having a problem at specific building the same VLAN is working fine at other buildings with same configuration. we are not using HREAP, its Local AP mode and all APS are ping able  from Controllers.

Thanks

[grabonlee]

APs pinging the contorller is different from the dhcp requests being able to reach the DHCP server as they are separate entities. No one knows your network setup, so it's better you provide a debug. There's no point beating about the bush.

[Faisal Shabbir]

Hi Osita,

i am getting the following message on one of the controllers:

IDS Signature attack detected. Signature Type: Standard, Name: NULL probe resp 1, Description: NULL Probe Response - Zero length SSID element, Track: per-Mac, Detecting AP Name: IAT-GF-AP03, Radio Type: 802.11b/g, Preced: 2, Hits: 1, Channel: 11, srcMac: 00:c2:97:08:57:76

in addition there is one more error message i ma getting on same controller:

Warning: Controller has detected its IP Address 10.10.xx.xx being used by a machine with MAC Address 64:ab:f5:91:2e:f2.

could you please explain the issue type and severity level ??? also if possible solution..

Many Thanks

[Saravanan Lakshmanan]

http://www.metasploit.com/modules/auxiliary/dos/wifi/probe_resp_null_ssid

Locate the deivces sending these messages and remove it or you can ignore it by increasing the threshold on the wIDS configuration for that particular signature. if it happens to be your own device then update the driver to latest and see that fixes this issue.

Looks like same IP is used for two different devices on that vlan, find the other device and change the ip.