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I cannot understand why 2 switches won't auto-negotiate or communicate at 10/1000 (1000Mbps) when connected directly together. But they will communicate at 10/1000 with other switches. Can anyone help me?

I have two Ubiquiti EdgeSwitch PoE switches (ES-24-500W and ES-16-150W)

If I link the two directly then the ports show no lights and the web interfaces show "No Link".

If I change the config of one of the ports (either switch) from "Auto Negotiate" to "100Mbps Full Duplex" then the direct link works fine (but not at full speed of course).

If I put the ports back to "Auto Negotiate" but put a cheap unmanaged switch (NetGear GS105) in between the two EdgeSwitches all switches/ports work immediately at full 10/1000.

Things I have tried/checked with no success:

  • Checked continuity on the link cable and all cables/patch panels - all pins working and straight through.
  • Tried bypassing any patch panels.
  • Tried different ports in both switches.
  • One of the switches (ES-16-150W) has been factory reset.
  • Both switches updated to the latest firmware.
codlord
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  • Have you tried a crossover cable? The datasheet sucks, no mention of *Auto MDI-X* (which would make a crossover cable unnecessary). – Zac67 Feb 20 '22 at 17:42
  • Yeah you are right nothing seems to state if it's Auto MDIX or not but I thought all Gigabit network stuff was as 10/1000 uses all cores etc. I don't really want to change the cable as it's sort of built-in to building. I could of course temporarily move the two switches together to try a crossover but if it turns out to be a cable issue I think the easier fix for me will be to use seemingly any other brand switch which all seem to work fine on this cable... I was just thinking/hoping it was some weird EdgeSwitch config issue. – codlord Feb 21 '22 at 18:04
  • Even though *most* 1000BASE-T ports support Auto MDI-X it's still optional. There are small crossover adapters you could try. Dunno about Ubiquity, some switches are configurable for MDI-X/MDI/Auto MDI-X and perhaps those switches just don't default to Auto MDI-X. – Zac67 Feb 21 '22 at 18:43

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