Cisco 7921g and Aerohive Networks.

  • 1
  • Question
  • Updated 5 years ago
  • Answered
Hi all!

Is there anyone here who has any experience with Aerohive in combination with Cisco 7921g phones? Everything looks healthy and mighty fine but for some reason quality remains iffy. It doesn't look like anything Aerohive so I wondered if anyone here has any ideas..

If anyone has any that'd be great!

Many thanks

Stefan
Photo of Stefan van der Wal

Stefan van der Wal, Champ

  • 70 Posts
  • 24 Reply Likes

Posted 5 years ago

  • 1
Photo of Crowdie

Crowdie, Champ

  • 972 Posts
  • 272 Reply Likes
A couple of pointers:

* Disable the lower 2.4 GHz data rates so the phone doesn't stay associated to an access point too long.

* You will need to limit the 2.4 GHz transmit power. To determine what the maximum 2.4 GHz transmit power should be complete some roaming tests between your access points. Generally, the closer you have the access points the lower you will need to make the maximum 2.4 GHz transmit power. If the phone does not roam correctly or you hear a short silence when roaming your 2.4 GHz transmit power is too high.

* If your building is multiple level be extremely careful to stop 2.4 GHz signal from one level propagating to another level.

* Ensure call admission control (CAC) is enabled. If it isn't you will experience performance issues when a number of phones with active calls associate to the same access point. This includes when a phone roams to the access point as the user walks through the area.

* Enable the SIP application layer gateway.

* Configure the QoS settings for the Cisco OUI.
Photo of Stefan van der Wal

Stefan van der Wal, Champ

  • 70 Posts
  • 24 Reply Likes
Hi Crowdie,

Thanks! I think the power is the problem, so I'm going to see if I can do anything with that. I've considered throwing the phones to the 802.11a band to stop the problems on the 802.11g band. But it somehow feels like a stupid idea.

I'll look at the application layer gateway and the QoS settings as well (I had QoS configured and it seems to work, but maybe it can work better).

Many thanks,

Stefan
Photo of Crowdie

Crowdie, Champ

  • 972 Posts
  • 272 Reply Likes
What is the channel utilisation like in the 2.4 GHz spectrum? I find that 2.4 GHz non-Wi-Fi interferers are a killer so moving to 5 GHz certainly helps that. The con of the 5 GHz spectrum is that the attenuation is twice that of the 2.4 GHz spectrum so you may need your access points to be closer than you would with a 2.4 GHz deployment.

On the 2.4 GHz transmit power front I have never been able to get SIP phones working correctly when the maximum 2.4 GHz transmit power is 20 dBm. If is also important to remember that the Aerohive radio management will only ever drop the transmit power 6 dBm below the maximum.
Photo of Stefan van der Wal

Stefan van der Wal, Champ

  • 70 Posts
  • 24 Reply Likes
Channel utilisation is well below 30% on average. It's a very clean spectrum for a change (School in the middle of a forest). The design for the school is on the 5ghz band for the use of n. So it may work.

I've also discussed this with the end user and I see room to reduce the transmit power well below 20. Would you recommend a set transmit power?
Photo of Crowdie

Crowdie, Champ

  • 972 Posts
  • 272 Reply Likes
There is no consistent answer but I tend to start at 17 dBm and head downwards as required. You may find that in one area of a building 17 dBm works but you have to drop down to 15 dBm or 11 dBm in other areas.
Photo of Stefan van der Wal

Stefan van der Wal, Champ

  • 70 Posts
  • 24 Reply Likes
Hi Crowdie,

Thanks for your help on this one earlier, We've moved the phones to 802.11a and it immediately cleared up the trouble. It seems that as soon as the phones see less AP's they are more efficient and working just peachy.