wall socket -> Ethernet cable -> moblab setup: moblab cannot detect ethernet |
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Issue description*buggy behavior* During my trials and failures I have realized that: My moblab (I tried 2 moblabs) have a hard time detecting Ethernet when I have this setup: wall socket (test network) -> ethernet cable -> moblab (thru RJ45 port) Moblab behavior: 1. At login screen, moblab cannot detect ethernet 2. At login screen, moblab can detect ethernet but cannot connect to it 3. In web UI, moblab cannot detect ethernet 4. In web UI, moblab can detect ethernet but cannot connect to it *workaround* I've found that the following setup works: 1. wall socket (test network) -> ethernet cable -> USB adapter -> moblab 2. wall socket (test network) -> ethernet cable -> switch -> ethernet cable -> moblab *other things* Since we don't have any other Chromebook with RJ45 port, I have not tried the setup on a Chromebook: wall socket (test network) -> ethernet cable -> DUT (thru RJ45 port) But, the following setup definitely works: wall socket (test network) -> ethernet cable -> USB adapter -> DUT
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Nov 27
Oh wait, this is on the moblab, not the DUT. I have no idea why adding a switch would help. Have you tried a different wall socket?
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Nov 27
Re ayatane@ I tried 2 wall sockets.
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Nov 27
+Grant for any insight on workaround or tips on root causing the original failure.
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Nov 27
We have many chromeboxes and "Chromebase" (all-in-one) which have built-in ethernet with RJ45 ports. This is not a new technology. The builtin RJ45 ports on Chromeboxes are the most reliable ethernet available. Almost certainly something is fishy with the switch or cabling connected on the inside of that "wall socket". I believe it's just "mere coincidence" that a particular USB adapter works more reliably than the builtin NIC. It's possible the latest moblab RJ45 ethernet phy signalling isn't tuned (e.g. signal output could be weaker or stronger or something). I've not tested/used the "fizz" machines very much that moblab is currently based on. Adding a switch between "wall RJ45 port" and chromebox means we've eliminated that cable run (in the wall) and don't have to directly talk to that switch. Either one could be suspect and small "unmanaged" switches are heavily tested to tolerate (and hide) all sorts of issues. I'd suggest to just keep using that switch. Most USB ethernet adapters aren't nearly as reliable as a switch. |
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Comment 1 by ayatane@chromium.org
, Nov 27