User De-authenticates every few minutes

Aug 24, 2007 5 Replies
O

Hello all,



One of our users gets de-authenticated every few minutes from our Cisco 1240AG APs. He is using a D-Link DWL-AG530 NIC. I do have Cisco Aironet extensions enabled on the AP.



Any ideas will be appreciated.



Here is the Log entry from the AP Mar 7 16:32:54.608 Information Interface Dot11Radio0, Station X Associated KEY_MGMT[NONE] Mar 7 16:32:52.305 Information Interface Dot11Radio0, Deauthenticating Station X Reason: Previous authentication no longer valid Mar 7 16:32:52.305 Warning Packet to client X reached max retries, removing the client



Thanks.



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L

This behavior could have different causes:

  • Radiowave interference
  • Layer 2 deauthentication attacks
  • Bruteforce attacks on the authentication key depending on the mechanism in use (MIC protects against this kind of attacks in WPA mode by kicking off clients for the duration of 1 minutes to reauthenticate themselves)

Best solution in my opinion is to find out the most probable cause by testing with the hardware in different rooms/buildings, running a wireless sniffer to inspect what is going on in the air and, if possible, elimate the cause of the disconnects.

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M
  1. What IOS version is running on AP ?

  1. What firmware version is installed for the D-LINK NIC NIC ?

  2. Using the D-LINK NIC utility, what is the signal strength seen by the D-LINK NIC ?

  1. How far are from the AP is the PC with D-LINK NIC ?

  2. Are there other PC's using the same type of NIC in your network ?

  1. Has a different type of wirless NIC been tried in the troubled PC ?

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O

12.3(11)JA

Don't have it at the moment

The signal strength is excellent as the AP is not too far from the PC.

About 15 feet

BTW, I updated the driver on the D-Link card and that fixed the issue. Thanks for the reply.

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M

is running on AP ?

To what driver version ?

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O

is running on AP ?

1.05
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