You configured a Versa speed-test server on a VOS device, but the client cannot start...

The correct answer is A . Versa link-bandwidth troubleshooting documentation explains that a VOS device can be configured as a Versa speed-test client, a Versa speed-test server, or both simultaneously. After the server is configured, the client starts the test by initiating a TCP-based connection toward the speed-test server. The server listens on port 5201 . The documentation includes an explicit note that if the VOS device is behind a firewall, port 5201 must be open .

This is different from the SD-WAN overlay data path, which commonly uses UDP-based transport encapsulation, and different from internet speed-test traffic, which uses other ports depending on the specific test type. In this scenario, the question states that a Versa speed-test server was configured, so the relevant requirement is TCP 5201 reachability from the client to the server.

TCP 443 may be used for management or web access, UDP 4790 is associated with SD-WAN transport encapsulation, and UDP 53 is DNS. None of those replace TCP 5201 for Versa speed-test server operation.