The screen capture function which is available on Cisco IP Phone models can be very useful, especially in some situations that require remote support. In the following article, you can find the procedure for taking screenshots for Cisco 7800 and 8800 series IP phones.
First, let’s verify some settings on Cisco Unified Communications Manager (CUCM).
CUCM Settings
In order to take a screenshot of a Cisco IP phone, the phone first must be paired with a CUCM user (End User) and web access must be enabled in the phone settings page. You can make these settings from the CUCM Administration page using the Device -> Phone menu and selecting the corresponding phone.
First you need to open the web interface of the phone. To do so, enable Web Access in the Product Specific Configuration Layout section.

Then we need to pair the IP phone with an end user. Select the end user in Owner User ID section on the same settings page.

After selecting the end user, select the relevant user from the User Management -> End User menu and ensure that the corresponding phone is added in the Controlled Devices field of Device Information section.

After applying these settings, go to System -> Enterprise Parameters menu and check the user authentication URLs that the phone will use when accessing the web interface. Related settings can be found in the Phone URL Parameters and Secure Phone URL Parameters.

Authentication on IP phones uses the URL format below:
http(s)://cucmcip/authenticate.jsp?UserID=<id>&Password=<password>&devicename=<nameofthedevice>
If the information entered is appropriate, browser displays a simple AUTHORIZED message, and if there is inconsistency in the information, UN-AUTHORIZED message is displayed. Below is a sample URL and its output:

Tip: If you want to by-pass authentication on IP phones, you can redirect the Authentication URLs under Enterprise Parameters to a webpage that will always respond as “AUTHORIZED” 🙂
Taking a Screenshot of a Cisco IP Phone From a Web Browser
If you have done all of the above steps properly, you can now take a screenshot of your IP phone. To do so, you can use the following URL:
http://cucmip/CGI/Screenshot
After entering the username and password, you will see an image like the following:
Troubleshooting
If you get an error message like this in your web browser:
<CiscoIPPhoneError Number=”4” />
This problem is probably related to authentication. Verify that the IP phone is in control of an end user and that the user’s credentials are correct. To see this easily, you can test and adapt the above authentication URL format to your phone. If the URL works but the phone’s web page still shows the same error, reset the phone and try again.
<CiscoIPPhoneError Number=”0” />
This error indicates that the phone cannot connect to the URL provided in CUCM for authentication. There can be many things that can cause this issue, and almost all of them are about the accessibility. Please check the settings like routing from IP telephones to CUCM (or authentication server), DNS etc.