7921 to 7921 Calls Have no audio with UC540 and AP541n

Question

We have a new deployment where we have 5 total 7921G wifi phones connected via 2 AP541n access points, one connected to a ESW520p switch and then to the UC540 and the other connected directly to the UC540.  The wifi phones are intermittently giving no audio when calling each other, however, calls to the PSTN consistently do have 2 way audio.  Is this a security issue perhaps?  We are running the latest CCA software pack as this is a brand new deployment, also the AP's were upgraded to the latest firmware. HELP.

Answer 1

I have also tested this scenario in the past and I found that phones associated to the same ap
did seem to have a higher incidence of the one-way audio condition but not every time.  We have 3 4404 controllers and I did note that every time I a complaint the phones involved were on the same controller.  I could not reproduce the problem EVER if the phones were associated to aps on different controllers, TAC assured me that this was unlikely related to the issue but I have my doubts.  Since upgrading the phones to the latest firmware 1
.3.4SR1 initially I was still getting complaints of the condition occuring so I decided to reboot the POE switches involved with the problem areas since they had in some cases been up for 2+ years, this was just a last ditch effort but for whatever reason that seems to have cleared up the issue.   I have not had the issue reoccur in the past 2 weeks since rebooting those switches, I also believe that some of the phones in question had not yet received the update and because of this I was getting false reports of upgraded phones still having the issue.  I found two seperate cases where one of the phones in question still had 1.3.3, after forcing the upgrade they were fine.  So first thing I would do is make sure the phones have 1.3.4SR1, then I would check to see how long the switches connected to your AP's have been up and also perhaps the IOS version, if they are Cisco switches it may not hurt to contact TAC and see if they can recommend an IOS that would be a good candidate.  Another thing to make sure is that your QoS settings on all the switches involved are set correctly.  We had tons of problems initially when we first started using the phones on the wireless network.  We thought our QoS was set correctly but what we found was there was some IOS bugs on some of the switches downstream that required special switchport commands to "fix".  Most dealt with the qos trust dscp command, some switches had to have the dscp tag and some had to have the cos tag, very strange and it took several CCIE's several days to come up with the final solution after many wireshark traces to make sure the QoS tags were making it all the way through.  
Watch, now that I am writing you that my problems seem to be fixed, I am sure Murphy will raise his ugly head and ruin my Friday