Dialer network diagnostics

Designed for network and security administrators, this tool verifies that the current workstation can reach all required voice and video call services and vendors.

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What this test cannot tell you

It cannot prove TLS inspection is happening. A browser has no access to the certificate chain, so an inspecting proxy is invisible to this page and can only ever be inferred.
It cannot scan the UDP media port range. It only observes the ports the vendors happened to offer during this run.
It has no DNS visibility. A name that does not resolve and a host that is firewalled look identical from here.
It cannot read the status of a blocked request, so a proxy returning 403 and a dropped connection are indistinguishable.
It cannot separate network blocking from a browser policy or extension doing the blocking.
It cannot test a bare IP address. The published vendor addresses accept TCP but refuse a TLS handshake without a matching hostname, and every method available to a web page needs that handshake to complete. Check those from a terminal with nc -zv <address> 443.
It covers this machine, this browser, on this network segment, at this moment. A pass here does not clear the whole site.