Unplugging network leads

[Mike Clarke]

I came across this dire warning in a manual for a Dell PC:

"CAUTION: To disconnect a network cable, first unplug the cable from your computer and then unplug the cable from the network device"

Well I've been merrily swapping out network leads for decades without any concern about which end to unplug first and don't expect to be changing my habits but was wondering if anyone had any idea why a manufacturer should come up with this sort of warning.

The icon beside the warning implies the risk of "potential damage to hardware or loss of data if instructions are not followed" but is not as drastic as the one implying "potential for property damage, personal injury, or death".

[Tim Watts]

Complete and total bollocks :)

[The Natural Philosopher]

Probably some EU regulation then.........in case you pull the computer off the table accidentally and brain damage a baby more than a state education will.

[Adrian Caspersz]

If your network device (say, a switch) has activity lights still flashing and you are "sure" you have unplugged your computer, you now have a clue to puzzle over, like are you staring at the right switch port?

If you do the move the other way round you might accidentally disconnect someone else.

or, yeah, complete balderdash ...

[John Rumm]

Its probably more a case of with a cable connected at one end only, and the other flapping about in free space, you have a (infinitesimally small) additional risk of damage to the end still connected to the cable, should the free end of the cable make contact with something it should not (electrically).

So by stipulating your end is disconnected first, you don tin knickers, and get to push any perceived risk elsewhere!

[Vir Campestris]

Ethernet ports are pretty well protected. They're actually designed to run with different earth levels and such like.

So I'll go with poppycock.

Andy

[Huge]

[25 lines snipped]

In the "good old days" of thick co-ax ethernet it was actually designed to continue working even if mains got onto the coax, somehow. Dunno if that's still the case with the modern stuff.

Me too.

[www.GymRatZ.co.uk]

What about a static discharge? I'm sure it might object to many 1000's of volts zapping it however unlikely it is.

[Andy Burns]

All pairs are transformer isolated, good to about 1500V, the magnetics can either be inside the 8P8C jack, or in a fat looking chip on the NIC/motherboard nearby.

[Huge]

Thanks. I assumed something like that would be the case!

[Graham.]

I never worked on 10Base5, but I saw plenty of 10Base2, and I assume it was much the same from the point of view of mains isolation, or rather lack of it. On more than one occasion I got a belt when disconnecting the cables from a T piece, because one of the machines in the chain was plugged into a mains supply with no earth. I imagine this could be far worse if the network encompassed offices on more than one phase of the mains, but thankfully I didn't ever have to deal with that.

Actually I did, but that wasn't Ethernet related.

[Mike Tomlinson]

En el artículo , Huge escribió:

It's isolated to 2kV. Still wouldn't like to try an etherkiller, though.

[dennis]

Its supposed to be. I blew up a Samsung TV when I plugged it into a PoE hub. It just started to smoke and the tuner didn't work afterwards. Nothing else has ever blown up when plugged into the hub. It should have been impossible for the DC to get past the transformers.

[Mike Tomlinson]

En el artículo , dennis@home.? escribió:

One batch of Raspberry Pis had to be re-worked after the Chinese supplier of the RJ45 ethernet socket omitted the transformers, or they fitted the wrong part at the factory, or something like that.

[Bob Eager]