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Friday
Sep212012

BUG CSCtt38270: 7925 sometimes takes 1+ second to respond to WPA M1 key message

Heads up if you're having wireless voice issues with 7925 handsets with WPA2/PSK. Problems with roaming, gap in voice bug.

7925 sometimes takes 1+ second to respond to WPA M1 key message
Symptom:
A wireless phone call may experience a voice gap of 1.5 - 2 seconds when it roams if using WPA2-PSK.

Conditions:
7925G is configured to use WPA2/AES PSK.

Workaround:
Configure some key management method to avoid performing a full WPA2 key exchange
at each roam time. For example, EAP with CCKM, or static WEP.
If using PSK, then reducing the WPA key retransmission timeout (e.g., on a WLC,
via "config advanced eap eapol-key-timeout 250", may ameliorate the problem
somewhat (e.g. bring the outage duration down from 2.5 to 1.7 seconds.)

1.4.3ES.1 containing the fix for CSCtz48689 may be helpful as well.

Further Problem Description:
A wireless packet capture, or a "debug client" on the WLC, will show that the WLC/AP
transmit the M1 key message to the phone (and the capture shows that the phone ACKs
it), but the phone does not send its M2 key. So the WLC/AP have to retransmit the M1 key,
till finally the phone responds.
Status Status 
Terminated 

Severity Severity 
3 - moderate 

Last Modified Last Modified 
In Last 2 weeks 

Product Product 
Cisco Unified IP Phone 7900 Series 

Technology Technology 
Wireless, Mobile 

1st Found-In 1st Found-in 
1.4(2)
1.4(1.1.1.7) 

 


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Reader Comments (1)

We worked with TAC on this one for a bit. They confirmed as best they could this is all flavors of PSK - WPA1/2 TKIP/AES. We have our EAPOL key timers at 250 ms by design already and when we saw this behavior it took the phone about 450 ms or so to roam. Not great for voice quality but better than a second or more.

Tac said the BU was not able reproduce this and they did not have a lot of resources committed to fixing it. We were planning on moving to 1X and cckm any way so we are moving that timeline up.

September 24, 2012 | Unregistered Commenterscotty1213

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