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I'm in a shared office space. I recently moved offices on the floor, which has 6 Ethernet wall ports grouped together, like below.

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I wanted to test internet connectivity for each of these ports. So I used a laptop with an Ethernet port, plugged it into each port, and pinged 8.8.8.8. I found 2/6 of the ports had connectivity. After verifying which ports worked, I connected my Netgear Nighthawk AC1900 router to one of the working ports. I then used a direct Ethernet connection from the router to my laptop. However, I didn't get any internet connectivity either wirelessly or via the direct connection to my laptop.

This is where things get very weird. I already verified which 2 ports had connectivity. So I unplugged the router, and did a direct connection from the Ethernet wall port to my laptop, as I had first done and verified connectivity. However, now my laptop has no connectivity either.

I followed the same process for the second working port. First I plug in the laptop directly, verify there is a connection. Then I unplug the laptop, plug in the router, and connect the laptop to the router. No connection. Then I unplug the router, plug back in the laptop, and the laptop now has no connection.

I'm boggled as to why plugging in a router to an Ethernet wall port would cause it to stop having giving a connection. Any advice or help would be appreciated.

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    If only two out of six ports work, how can you be so sure that the remaining two ports are stable?
    – MMM
    Commented Jan 10, 2020 at 15:44
  • So if the ports are unstable, what's my next step? I would go to the building manager, ask to go to their IDF room, and then I trace the cables to the ports in the office. I find the cables are all connected. Then what do I do to make the ports stable?
    – Alex F
    Commented Jan 10, 2020 at 15:51
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    Wouldn't hurt checking if the cables are installed correctly in the outlet. It's also possible the cables themselves are damaged but depending on their length that might be really hard to debug
    – MMM
    Commented Jan 10, 2020 at 15:55
  • 3
    If your network uses managed switches, it's entirely possible that "port security" is set, and when an "unauthorized" MAC is seen, the switch disables the port. I see this in my organization all the time; it is deliberately set to prevent users from connecting their personal devices, or moving devices from location to location without authorization from IT. Contact your network administrator and inquire.
    – Jeff Zeitlin
    Commented Jan 10, 2020 at 16:00
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    To add to what Jeff said, managed switches can also disable ports if they see Spanning Tree Protocol (STP) packets (also called BPDUs), or if they see something acting as a DHCP server, or if they detect a network loop. So if your router had STP enabled, or if it was providing DHCP service on its port that you connected to the wall jack, or if you connected two ports from the router to the wall at the same time, the ports may have been disabled for one of those reasons. You IT folks should be able to see why the ports were auto-disabled and re-enable them.
    – Spiff
    Commented Jan 10, 2020 at 16:15

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