Cisco 8851 handset display flickering

[rowdygardner]

We are having issues with our 1000+ Cisco 8851 handsets that are on Webex Calling where the line button, call park buttons and softkeys flicker and random times on the screen. The Date, Time, Cloud and Speed Dials stay solid, but the other buttons go off/on multiple times per second.

This occurs for a few seconds up to 5 minutes during which the phone won't ring, the call gets disconnected or causes the phone to continue ringing after someone else has answered it. This problem is happening at all 150 of our sites and we have no idea why.

I've uploaded some videos of the issue occurring on our phones.

Has anyone ever experienced this issue before? If so, what did you do to resolve it?

[daault]

It sounds like you're encountering a technical issue with your Cisco setup. It's definitely important to get this sorted out, especially if it appears to be a bug. Opening a support case with Cisco Support is the right move here. They have dedicated teams to help troubleshoot and resolve these kinds of issues.

To ensure the process goes smoothly, it's a good idea to gather as much relevant information as possible. That includes obtaining a debug level PRT and a packet capture. These will provide valuable insights for the support team to diagnose the problem effectively.

Here are the steps you can take:

1. Obtain a Debug Level PRT: You can follow the instructions provided in the link you shared to configure the debug level in your MPP phones.

2. Packet Capture: Capture packets related to the issue so that the support team can analyze the network traffic and pinpoint the problem.

3. Open a Support Case: Use the Support Case Manager link provided to initiate the support process. Make sure to include details such as your ORG ID and MAC address of the affected device(s). This will help the support team locate your setup quickly and efficiently.

Remember, Cisco Support is there to assist you, so don't hesitate to reach out to them. They have the expertise and resources to get to the bottom of this issue and provide you with the necessary assistance.

[daault]

Debug Level PRT: https://www.cisco.com/c/en/us/support/docs/collaboration-endpoints/ip-phone-8851/218093-configure-debug-level-in-mpp-phones-regi.html
Support Case Manager: https://mycase.cloudapps.cisco.com/attendeeCaseCreate

[Vencola]

Have you found the solution, I have a similar problem 

[rowdygardner]

I am very disappointed that nobody from the Webex community replied to my post about the display flickering on the Cisco 8851 handsets. I also had the same problems when dealing with Webex support as well as their partners. They all keep saying it's a network issue but don't offer any solutions.

We've discovered that the problem is actually due to "DNS Proxy" being enabled on our SD-WAN appliances. Once this was turned off, the problem went away. 

I suggest that Webex add this to their documentation and pre-implementation steps to ensure that DNS Proxy is turned off on the network before installing any desk phones which connect to Webex.

[rowdygardner]

Here is another video of the issue.

[rowdygardner]

Here is a video of the issue