Ethernet

How it tests

A hands-on test of its own. The tester plugs a cable from a router or switch into the Mac's own port (a port the Network screen turned off comes back on). It waits for a link and an IPv4 address (20 s), then runs the same boot.watch test over that interface alone, with the counters cross-check. An adapter on USB or Thunderbolt is shown but decides nothing: only the built-in port counts. The quick pass only reports the port and its link.

How it decides

Supported: an address, at least 256 KB down and 64 KB up verified over the port, counters agreeing. Partial: an address but the data won't flow while boot.watch answers. Failed: no driver or no interface, or “It's plugged in, no link” (offered after 10 s). Not tested (uncertain): a link without an address, the only link with nothing working over it, a sign-in page, counters short. Not tested (other): boot.watch down or busy, or the clock off. No equipment: skipped.

How sure it is

Data checked both ways over the port proves traffic flows, not only a link. USB and Thunderbolt Ethernet adapters don't count.

What could mislead it

• Could fail when it shouldn'tA bad cable or a dead switch port reads as “It's plugged in, no link”: failed.
• Could end without a verdictThe only link with nothing working over it may be a network with no way out, so it's not tested (uncertain), not partial.