I have recently inherited a deployment of 18 Cisco 520G Series Access Points at an educational facility. The facility was experiencing significant dropouts of the wireless connection from both laptops and desktops, resulting in substantial imapact to both the teachers and students working practices. After an exhaustive site survey, it has been ascertained that 7 of the Access Points were not required and subsequently their wireless radios have been switched. To complete the solution, the AP's were setup on non overlapping channels (1, 6, 11) with an analyser used to confirm percentage overlaps and excellent coverage throughout.
Since the completion of the survey and the configuration of the AP's, the facility has benefited from a more robust wireless solution and a wider signal throughout. However, there are a number of machines (desktops with Linksys and Dlink wireless PCI cards) which experience wireless dropouts and are disconnected from the network. The disconnection lasts approximately 30 seconds before reconnecting again. When i subsequently view the Wireless AP logs i can see the following alerts -
Packet to client 0018.3919.1a2b reached max retries, removing the client
Interface Dot11Radio0, Deauthenticating Station 0018.3919.1a2b Reason: Previous authentication no longer valid
Interface Dot11Radio0, Station 0018.3919.1a2b Associated KEY_MGMT[WPA PSK]
These alerts occur several times within an hour and apper to be directly proportionate to the amount of traffic you push through the Wireless Cards. I can quite simply force a disconnect from the client machines by running an RDP session to a local server, and begin to perform AD tasks etc. There is 20 seconds between the first alert and the third alert meaning there is roughly, 30 seconds before the client has connected back to the network and is operational again. In an attempt to reduce the number of times these errors occur, i have attempted to increase the Request to Send setting on the AP's to 128 from 64. This has made little to no difference as to the amount of times the clients are disconnected.
I have been unable to find any other cause for the disconnects on the AP's themselves, therefore i have begun to look at the individual cards and there appropriate drivers. Unfortunately, both of the Linksys and D-Link cards are significantly old and therefore driver support is limited. Both are however set to low roaming aggressiveness.
As a final spanner in the works, I have a Dell E6410 laptop with an Intel 6400 Wireless Card, which does not suffer from any of the problems the client machines experience. Regardless of the tests I perform from the laptop, it remains connected to the Wireless throughout.
Before I purchase a test intel card for one of the client machines, i would like to know if there is anything else i could look for from the AP side, or if there is anybody who has experienced similar symptons.
Transferring Crash file from standby: Login to the Active WLC in HA.
From CLI: (Cisco Controller) >transfer upload datatype crash (Cisco
Controller) >transfer upload filename (Cisco
Controller) >transfer upload mode tftp (Cisco Controller) >transfer
This is the start of a display filter cross reference between Wireshark
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