• Is superceded by SOLVED!, 26 Nov 2019

Continuing network frustration

Volume 3, Issue 36; 26 Nov 2019

It still doesn’t work, and it’s worse than I thought. Help!?

A while back, I expressed bafflement at the behavior of my network. Short story: if my laptop is plugged into the wired network, everything is fine. If it isn’t, half the network doesn’t work.

Initially, I assumed this had something to do with Pi-hole running on a Raspberry Pi and that it was somehow DNS (i.e. Pi-Hole) related (it doesn’t, it isn’t). I’ve been mostly ignoring the problem (because mostly my laptop is plugged in).

But last night, I got frustrated and poked at it again. I’m stumped and I’m going to rip everything apart on Thursday and debug the [expletive deleted] out of it. I’m going to take every component out of the closet and methodically test the combinations.

But before I do that, a Hail Mary pass in case some network savvy reader spots the problem.

  • I have a Netgear Nightawk X4S R7800 router. It’s running OpenWrt 18.06.2.
  • There’s also a hub because I have more than four wired connections:
    • A Sonos boost
    • A couple of Raspberry Pis.
    • A Philips Hue bridge
    • A QNAP NAS
    • An HP printer
    • And my laptop
  • There are also a multitude of wireless connections:
    • Several Sonos components
    • A couple of tablets
    • A phone
    • A Roku
    • And my laptop

I’m running an app on the Android tablet that displays connectivity on the local network (the problem has nothing to do with that tablet, AFAICT, it’s just a useful way of observing the state of the network). If my laptop is plugged into the wired network, it can see everything. If I disconnect the wired connection, The wired devices fall off the network.

And I don’t just mean from the perspective of the wireless devices. The wired devices simply can’t use the network.

If I go back to one of the Pis, for example, that’s got a wired connection, it can’t ping the Internet, or other wired devices on the network (even one’s plugged into the same router), or, for that matter, the router!

But my laptop can.

Some notes, things I’ve tried, random observations.

  1. I replaced the router. It didn’t help.
  2. The previous router was running dd-wrt and exhibited the same problems, so I don’t think it’s a borked OpenWrt config.
  3. When the Pi was thought to be the culprit, it was suggested that the on-board ethernet might not be up to scratch. I plugged in a USB-to-ethernet dongle. No change.
  4. If I give one of the Pis both a wired and a wireless connection, that doesn’t help. (Either the network at large or the connectivity from that Pi when my laptop is unplugged.)
  5. Removing Pi-Hole from the equation doesn’t help.
  6. Removing the wired hub from the equation doesn’t help.
  7. Putting a different laptop on my desk doesn’t help.

I do not trust the narrator. I assume that some of what I just described is not true: that in my frustration and ad hoc testing, I’ve missed some clue. Or that my descriptions are inaccurate and/or that I’ve leapt to incorrect conclusions based on my limited and naive understanding of networking. What I’ve just described simply doesn’t make sense to me.

If it makes sense to you, any kind of sense at all, please do tell!


Define 'half the network doesn't work' please? Wireless half? routing half? wired half? Other half? Long while back I loaded a network 'analysis' tool, showed what was happening? I'll see if I can find it again.

—Posted by Dave Pawson on 26 Nov 2019 @ 04:03 UTC #

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