a guess question

RouterOS General
1

Hello, a guess question :slight_smile:
I have a network made of two switches

Core Router -->Switch+network -->Switch2+network

Network is the same in both cases, the second switch is just an extension to another building. The cable that connects the two switches is some 120 meters long.
What happens is that some time the second switch gets completely frozen, no communication. It does not happen often, very rarely. When it freezes the only way to bring it up is actually turn it off, disconnect all cables, turn it on with no cable on it, than start putting cables one after another. A simple restart of it doesn’t work.
Two days ago it happened to the first switch, same behavior and same solution. Strangely enough during this kind of freezes, I can see with winbox the mac address of the router but can not connect to it.
I can not work out what could possibly cause it, I presume some packet generated by some PC on the network that remains alive even if switch is turned off.

What do you think could possibly cause this?

2

Maximum recommended CAT5 length is 100 meters. Maybe that could be causing the problem?

3

Yes, I know that, but it still connects. I have once even done a 160 meters long :slight_smile: (good quality cable). How can the cable influence it? Maybe you are right, maybe some kind of electrical field or something (I am no electrical specialist) which goes back and forth. But if I turn off one switch there should be no current running on the cable, right?

4

If the cable is not shielded, it could become a 120 meter antenna. I don’t think it would take much current to create enough voltage to mess up the switch. But that would depend on the input impedance of the switch.

That was just a thought. A friend of mine used to say “I would rather be lucky than good”. I don’t follow that mantra.