Prequalifying service availability for a customer involves the important step of confirming that their network is ready for the Webex Calling Services.

CScan is a network readiness tool designed to pre-qualify a customer’s network. Cisco customers can run this tool to test their network connection to ensure they get high-quality experience for their Webex Calling service.

Before you begin

A correctly configured firewall is essential for a successful Webex Calling deployment. Outbound ports are required to be open for signaling, media and network connectivity and local gateway because Webex Calling is a global service. Consult the Port Reference Information for Cisco Webex Calling Service to ensure that all required firewall rules are in place when running CScan tool.

Run your CScan test from the same network that you will use your Webex Calling services to get optimal results.

It is not possible to test every requirement from a web-based tool. Here are some areas which CScan cannot test or detect.

  • Whether user is using a wired or wireless network

  • Availability of a DHCP and DNS server

  • SRV support

  • NTP port for date/time synchronization

  • Proxies

  • QoS (TOS/DSCP)

  • VPN

Launching and Running a CScan Test


From the customer view in, go to Quick Links and select Webex Calling Network Readiness Tool. OR You can also access the CScan tool by going to and follow further instructions mentioned below.


Select a location, pick your home region, and choose a language.

Choose the location that is closest to you. This will be the data center that Webex Calling will connect to. If you are unsure, leave it to default selection.


Choose the type of test that you'd like to run

  • Advanced Diagnostic Test
  • Basic Test


Detailed information about each of these test types is available in the "CScan Report Information" section.

If you choose Advanced Diagnostic Test, you must allow CScan to access your microphone and camera.


Select the option box (by checking or unchecking) if you would like to share your information with Cisco and then Click on Start Test button to continue.


Cisco only collects your IP address and the test results to help troubleshoot your connection. Cisco will never send your information to 3rd parties.


Click “Continue to advanced test” button to initiate the test. Allow “Camera” & “Microphone access”. On the other hand, clicking the “Close” button would take you to re pick your kind of test.


Click on Start Test.


Want to see how it's done? Watch this video demonstration to see how to run a CScan test and how to interpret and save the results.

CScan Report Information

CScan runs a series of Basic & Advanced tests on port & bandwidth requirements to ensure a customer’s network is ready to deploy Webex calling services.

Basic Test

The Basic Test analyzes the following between your computer and the Calling services data center:

  • Concurrent calls estimate

  • Download and upload bandwidth

  • Latency (RTT)

  • Traceroute reports

  • TCP ports*

* The TCP ports that are tested are a subset of the ports required for Webex Calling. It isn’t possible to test all the ports for a web-based application. Follow the port requirements guide to ensure that your firewall is set up correctly.

Advanced Diagnostic Test

The Advanced Diagnostic test collects the same information as the Basic test and on top of that adds the following:

  • Packet loss (download and upload)

  • Jitter (download and upload)

To carry out the Advanced Diagnostic test, CScan must open a WebRTC connection to your computer, this requires access to your computer’s camera and microphone. CScan doesn’t save any audio or video packets. This permission is used for measuring packet loss and jitter. CScan will never access your camera or microphone outside of running a test. The permission is saved by your browser and can be revoked at any time.

CScan doesn’t test a wider UDP port range using WebRTC because of browser limitations, it can only validate two UDP ports for a test and it picks a random port range between 19560-65535 and then runs the test.

Traceroute Report

A traceroute report is provided every time you run a CScan test. To generate this, CScan initiates a reverse traceroute from a Webex Calling data center to the public IP address of your computer. This can give insight into where issues might be occurring along the path between your computer and the Webex Calling data center.

The reason for using the reverse traceroute option is that we can’t initiate a ‘normal’ traceroute from the client browser to the Webex calling service DC. Reverse traceroute reports can take a while to generate, and the link is greyed out until the report finishes generating.

Interpret Test Results

CScan tool estimates potential concurrent calls that could traverse your network. This is a conservative estimate based on the bandwidth that is required for audio calls, allowing for a buffer of extra internet traffic. Since the CScan test is taken at a single point in time, this is an estimate and not a guarantee of performance during peak traffic times.

Call concurrency is calculated assuming 50% overhead of other traffic on the customer network and by assuming all audio calls require two legs of approximately 100kbps & 50 packets/sec for each leg.

If CScan indicates that ports are blocked, check your firewall configuration and the port requirements document. If ports are blocked, you may have issues registering devices or making calls. It's not possible to test all ports listed in the Port Requirements document, so if all ports on CScan are listed as open, there may still be other ports not tested that are causing issues.

If latency or bandwidth figures are low, you may have a lower quality Webex Calling experience. Ensure you have enough bandwidth from your ISP, and that your device has a strong connection to the internet. If you’re using Wi-Fi, ensure that your signal is strong.

CScan test results can be viewed as Downloadable in PDF formats. Once the test execution is complete click on the "Download this report" and "Download traceroute report" links.

Troubleshooting Examples

Example 1

The figure below indicates that the CScan tool was unable to establish a UDP connection from the customer location to the Webex Calling service. This may be due to a NAT/firewall blocking the UDP traffic.

Example 2

The figure below indicates that the CScan test failed to establish SIP over TCP connectivity via port 8934 to the Webex Calling service. This may cause phone registration failures.

Example 3

The figure below indicates that the CScan test identified high latency and outbound packet loss. This may be due to possible traffic congestion on the WAN side or Bandwidth limitations at the customer location.