Wireless IP phones roaming problems (one way audio)

Answered Question
Mar 27th, 2008


i have a site with 8 1240AG APs and several 7920s and 7921s.

APs are running 12.3(8)JEA.

Sometimes I have one way audio between the IPPhones. After debugging i found out the following:

Sometimes (!)when a client is leaving an AP, AP-1 for example, and gets associated with AP-2, AP-2 sends the IAPP Sent Disassociation Notice to the other APs;

AP-1 receives the IAPP: Rcvd Disassociation Notice but does not disassosiates the client!

So, 7920 is on AP-2 but AP-1 thinks it is on itself, therefore does not send the IP packets to the new AP and we have one-way audio!

What could be going wrong?

APs are connected on a 2960 Cisco switch without vlan configuration.

The same problems exists at another site with similar configuration (1242 & 7920).


I have this problem too.
0 votes
Correct Answer by migilles about 8 years 6 months ago

Was a bug w/ IAPP fixed in 12.3(8)JEA2.

Also recommend to use 3.02 for 7920 and 1.1(1) for the 7921.

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Overall Rating: 5 (1 ratings)
irisrios Wed, 04/02/2008 - 07:05

It is recommended to enable Dynamic Transmit Power Control (DTPC) on the Access Point (AP) by using the Limit Client Power field in the user interface to ensure that APs and Clients are using the same transmit power. Also ensure that NAT or firewall is not blocking the RTP protocol used for voice communications.

Correct Answer
migilles Wed, 04/02/2008 - 11:48

Was a bug w/ IAPP fixed in 12.3(8)JEA2.

Also recommend to use 3.02 for 7920 and 1.1(1) for the 7921.

meggerman Thu, 04/03/2008 - 02:01

Where do you set DTPC ? i assumeon the WLC but where is the limit client power field ?

also we experience this and it appears that the clients are not roaming exactly in the same way g.nikitas has mentioned.

we can move to 1.1.1 in the meantime can you tell me how to set the above.

many thanks


victorgarciaternero Thu, 06/12/2008 - 00:56

I have the same issue. I have upgraded Aironet 1242 IOS (124-10b.JA3) and the 7921 firmware (1.1(1)), but I can't see any change. The call manager is 5.1.


meggerman Thu, 06/12/2008 - 01:45


check mobility groups are same over the controllers. check channel assignment is correct and there is a decent overlap but no co-channel interference.



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