Cisco Wi-Fi Phones 8821 won't connect with 802.11a/c ?

[Marco Matera]

Hi,

i have the problem that my Cisco 8821 won't connect with protocol 802.11 a/c. All 8821 Phones connect with 802.11a/n? 

802.11a/c is enabled on the WLC and i tried several WLC Versions 8.0 / 8.3.....

We use the Cisco 2702 Access Points. 

The VoIP SSID is configured with WPA2 (AES) and CCKM.

All other Devices  such as Notebooks, IPhone's and IPad's on another SSID (WPA2 with AES)  are connected with 802.11 a/c Protocol.

I can't find a option to enable 802.11 a/c in the CUCM or Phone?

[pieterh]

why would you need a/c ? voice is 64Kbps

apart from that, have you tried this:
Open a web browser and enter the following URL, where IP_address is the IP address of the Cisco IP Phone:
https://<IP_address>:8443
- 802.11 mode -> Select the mode required.

[Marco Matera]

hi pieterh,

thx for your answer but under 802.11-Mode you can only choose between 2,4 and 5 Ghz and not between b/g or n or ac. That means the phone decides which protocol is available in the Wireless LAN. 

It's not only about the 64kbps. It's also about

Increased speed and more clients on one ap
Higher speeds over longer distances
Beamforming
256-QAM Modulation / Channel occupancy

[Leo Laohoo]

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@Marco Matera wrote:

It's not only about the 64kbps. It's also about

Increased speed and more clients on one ap
Higher speeds over longer distances
Beamforming
256-QAM Modulation / Channel occupancy

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The above statement(s) doesn't make sense.   

Why would an IP Phone want "high speed" and "beamforming" when it does nothing but voice calls?  Is the phone doing video calls?  No.  Is the phone pushing any emails?  No.  

Another thing, with 802.11ac enabled the coverage area shrinks.  Is there adequate coverage area to really, really do 802.11ac? 

"Higher speeds over long distances"?  I don't think so.  This is just purely sales talk.  

And finally, CPU and battery life.  If the phone can really do 802.11ac, you'll need to use asbestos gloves to hold on to the phone because the CPU is going to boil.  The phone doesn't have CPU power nor the battery life to push 802.11ac.  

8821 can do 2.4 Ghz or 5.0 Ghz and as long as it can "choose" which radio to use and can roam between APs better than the 7925/7926 then rest is just sales talk.  

[Marco Matera]

But this does not answer my question.

The 8821 is sold with a a/c chip. My question is why they don't connect with a/c and only with a/n.

Yes we have the coverage for a/c. The fact is that we have a Cisco 2702e Infrastructure with

WLC Version 8.3 and Cisco 8821 Phones and the phones connect with a/n. I will ask my cisco account manager.

If i buy a car with 6 gears and i can use only 5 then i ask the seller why i can only use 5 gears and he will tell me you don't need 6 gears....

[pieterh]

I can see Marco's point.

what I wanted to say is the phone does not NEED a/c to function properly.

But I understand the concern that the phone is a/c capable, why doesn't it use this?

@marco, the AP is serving a/c to other clients, so YES you are using the 6th gear, but not for the city-bike that only has 3 :-) .

the AP offers , wifi bands, speeds / MCS rates, the client selects one.

The phone does not know all of the current a/c functionality as beamforming and MIMO.

I suggest to start and  check in the wireless settings if some (lower) MCS rates on a/c are disabled?

so the phone cannot find a match with the rates offered?
If so, enable the lowest and see if the phone then connects on a/c.

from the datasheet

Data rates

●  802.11a: 6, 9, 12, 18, 24, 36, 48, and 54 Mbps ●  802.11b: 1, 2, 5.5, and 11 Mbps ●  802.11g: 6, 9, 12, 18, 24, 36, 48, and 54 Mbps ●  802.11n: HT MCS 0, MCS 1, MCS 2, MCS 3, MCS 4, MCS 5, MCS 6, and MCS 7 ●  802.11ac: VHT MCS 0, MCS 1, MCS 2, MCS 3, MCS 4, MCS 5, MCS 6, MCS 7, MCS 8, and MCS 9 (MCS 9 available with VHT40 and VHT80 only)

[Leo Laohoo]

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@Marco Matera wrote:

The VoIP SSID is configured with WPA2 (AES) and CCKM.

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Hold on.  This is wrong. This should be WPA2 AES/PSK.  

[Marco Matera]

Hi Leo,

thx for the answer. Are you sure why is a pre-shared key needed to use 802.11 a/c? 

On another SSID with WPA2 (AES) and 802.1x + FT (Fast Transition) all clients can connect with a/c.

I cannot imagine that the protocol a/c or a/n has dependencies with the key management psk, cckm or 802.1x.

[Leo Laohoo]

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@Marco Matera wrote:

Are you sure why is a pre-shared key needed to use 802.11 a/c? 

---

It is for something else.  I got ruffled.  

What is the firmware of the phone?  

[Marco Matera]

on a cisco 2802 it's working as it should with cckm and same release and configuration all phones are connected with a/c that means it's a issue between cisco 2702 and 8821 phones.

[pieterh]

start the phones WLAN Diagnostics

this shows the phones information/capabilities

and also the rates offered by the access-point(s) 

[Marco Matera]

[pieterh]

what I read from this output:

so the AP requires Basic rate 12 and accept optional rate 18, 24, 36,48,54

the phone supports HT  (=802.11/n)  rate 0 - 23
the phone supports VHT (=802.11a/c) rate 0-9

=> match on /n but no-match on a/c !!!!!

[Marco Matera]

I found the problem...

our voice ssid is configured with FlexConnect Local Auth when i switch back to central auth (WLC) then the phone connects with a/c.