Long ago, I was in a university computer lab where we had... interesting wiring. Apparently, the signal in thicknet is the same as the signal in thinnet and some engineering student had created what looked like a terminator for thicknet and thinnet smashed together... a barrel connector with 10b5 on one side and 10b2 on the other. This was obviously not anything resembling a best practice in any sense of the word.
This worked, for some definition of worked. Thicknet was a bit pickier about the standing wave in the wire than thinnet was, but we had a thicknet cable that went along one wall, this connector, and then thinnet on the other wall.
The problem occurred when we added machines to the thinnet side because we wouldn't get the standing wave right and machines would disappear from the network until we got the right combination of lengths of wire between the thinnet T plugs.
There was one machine (lets say it was at 10.10.10.10) that was plugged into a different part of the network (the 10bT part) so was completely unaffected by all of the other network changes. When we would add (or remove) machines from the network, we would set up:
ping -f 10.10.10.10 > /dev/audio
As long as packets are flowing to the machine, the speaker was making noise. Network not visible for that machine and its silent.
And then go about trying different cables. When all of the machines were chattering away, we were done.