Cisco Webex Wireless Phone 800 Series - connectivitiy issues with ISE

[pescla]

We aquired a 840 and 860 Webex Wifi Phone recently to test. We have an internal WiFi that is secured via certificates from ISE.

From the very start we had big issues with the two phones - our Windows PCs run just fine on the WiFi, but the phones lose connection very quick.

First the phones connect OK, are registered with CUCM just fine. But after a few minutes, they lose connection to the WiFi, and are unable to reconnect whatsoever - except sometimes, where they are randomly reconnecting just fine.

I tried reinstalling the certificate on the phone, rebooting, readding the wifi, nothing helps. On ISE, i get those two errors:

5440 Endpoint abandoned EAP session and started new

11514 Unexpectedly received empty TLS message; treating as a rejection by the client

they are using two different certificates.

[Leo Laohoo]

Try something easy first:  Can the phones hold a stable WiFi connection with, say, PSK? 

NOTE:  Cisco Webex Wireless Phone 840/860 are re-badged of the Spectralink 95/96 series phones.  

[pescla]

@Leo Laohoo Yes, the connection to our guest WiFi did not have any of these issues

@Arshad Safrullai know for sure that the wifi itself is not the problem, as plenty other devices in the same area use it without any issues every day - i will forward what you said to our WiFi team, it sounds like a hint at least, thanks!

[Leo Laohoo]

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@pescla wrote:

@Leo Laohoo Yes, the connection to our guest WiFi did not have any of these issues

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Get Cisco TAC/WNBU involved.  
The phones are re-badge of the Spectralink 95/96 series phones and those phones are ever-so-reliable.  The only difference between the two is the software loaded in the Cisco Wireless Phone 840/860 are proprietary.  

If the Cisco Wireless Phone 840/860 only work with PSK, then it it is obviously a bug with the firmware.

[Arshad Safrulla]

Which wireless frequency band phone is connecting to (2.4 or 5)? It is always recommended that phones use 5GHz and have the lowest channel width setup. You can advertise your Voice SSID only in 5GHz band.

Did you do a RF survey when designing the Wireless network for Webex phones? Do you have minimum of -67 secondary coverage in a given area? Always conduct a RF survey before deciding to use any VOIP clients in your network

Did you check when the phone was disconnected it was in DFS channels? If yes plan your RF profiles to exclude the DFS hit channels. Also make sure that you have disabled lower data rates in your RF profile.

If you are using EAP-TLS it is recommended that u enable 802.11r FT. keep in mind WPA3 is not supported by these phones.