Information on our 7920 inmplementation

[computerhighguy]

I just thought I would share our expereinces with the pilot of our 7920 phones on our network. We just finnished it up and are excited to start rolling it out as secondary phones for certain level 2 techs who need to travel around the building. It took a long time and lot of troubleshooting to compile this information (and many hours talking with the TAC), but it has been worth it. If anyone else has any comments on thier implementation, I would love to here them. BTW, we are running CCM 4.01 (although we did most of our testing on 3.3(3)) and 7920 firmware version 1.07 (the latest at the time of this writing).

Site Survey:
1) SNR should be a max of 25
2) 1% max packet loss
3) 11 MB needed
4) A G radio network works very well


Access Points:
1) QBSS enabled on all APs.
2) AP Coverage should overlap 15% to 20%. Any more and the phones will not roam properly.
3) ARP Caching should be enabled on all APs
4) Channels should be set to non-overlapping and must be 1,6, or 11
5) All APs must support 11MB
6) QoS for ef and af31 priority 6
7) Keep the power low. High power is not necessarily good. I changed from 100mW to 30mW and voice quality increased greatly. Any more and the phones will not roam properly.
8) LEAP authentication on the voice vlan with key rotation every 1000 seconds


7920 Phone:
1) Same transmit power on AP and phones (except the phones don't support 30mW so we set it to 50mW). If AP power varies, set phone to highest AP transmit power
2) Ensure that RSSI is above 35 and CU below 20 (7920 site survey)
3) RSSI Threshold to 15
4) LEAP authentication
5) Phones seem to have a proprietary 2.5mm headset jack. I would look into this prior to pilot to ensure you are OK with not having headsets or being restricted to a few different kinds.


Gateway
1) ip precedence 6 on all VoIP dial peers
2) Disable Voice Activity Detection (no vad) on each VoIP dial peer. You can get a a loud clicking noise if VAD is enabled. If the WLAN network is designed properly, you do not need to conserve bandwidth. Use G radios.



It is what it is!!
__________________________________
A+, Net+, I-Net+, Certified Web Master, MCP, MCSA, MCSE, CCNA, CCDA, and few others (I got bored one day)

 

[simonxts]

computerhighguy,

I've done several wireless IPT imeplementations with Cisco and Spectralink so I'm just curious. What kind/type of AP's are you using? With witch software version? And how many of them have you deployed?
Do you have data as well as voice clients?

simon

 

[computerhighguy]

Cisco 1231 IOS AP with G radios
AP=12.2(15)JA
7920=1.07
About 20 have been deployed
We have both. Actually we have 5 VLANs and we support both data and voice on them. Everyone here has a laptop and if they are not in thier docking station, they are probably using one of the wireless vlans. I would like to make 1 correction to the above.


SNR should be a min of 25.


It is what it is!!
__________________________________
A+, Net+, I-Net+, Certified Web Master, MCP, MCSA, MCSE, CCNA, CCDA, and few others (I got bored one day)

 

[olivher]

computerhihghguy,
Did you experience any fast busy problems with the 7920? We're having a sporadic problem when the 7920 will ring, but when you or the other end answer, the 7920 produces a fast busy signal which both parties hear. TAC is currently working with me on this, but was wondering if you have come across this as we see to both have the same setup.

 

[computerhighguy]

I have not expereinced anything like that. We just started experiencing an issue where, intermittantly, when you answer with the 7920, you cannot hear the person on the end. Looks like TAC has this listed as a known bug. They think they have an engineering special that will fix it. Other than that, running great. We are very excited about this and its potential. Man I love this Cisco phone system. We are finishing up a migration from a Telrad system (made in Isreal). The old PBX is such a POS. Reliable, but no features. The biggest complaint we have was support from the manufacturer (pretty much non-existant).


It is what it is!!
__________________________________
A+, Net+, I-Net+, Certified Web Master, MCP, MCSA, MCSE, CCNA, CCDA, and few others (I got bored one day)