[c-nsp] Galvanic isolation for Ethernet?

[Victor Sudakov]

Charles Sprickman wrote:
> 
> > Scott Granados wrote:
> >> This problem sounds a lot like a dissimilar grounding issue.  Sounds
> >> like a potential between buildings is causing problems.  I don?t
> >> know if this is feasible but a common ground might solve some of the
> >> problems.
> >> 
> > Our electricians say that everything is correct, that all the
> > grounding circuits are interconnected and they measure their
> > parameters annually. I lack the necessary qualification to call them
> > liars (even if they are lying which I doubt).
> 
> It still might be interesting next time you have a failure to put a
> voltmeter between the switch chassis ground and each pin on the
> ethernet cable that blew the port.  If you see anything measurable
> that might at least tell you if its something like a transient
> lightning-induced spike or a weird grounding issue (I think).

If there is something, it must be transient. I have had it measured
and it's exactly zero.

> 
> OT, but long ago I worked at an ISP where we once had a few hundred
> phone lines going to modems and the lines ran up the buildings
> freight elevator shaft.  Each time someone had a freight elevator
> delivery you could hear the sound of a bunch of modem relays
> clicking as a bunch of users were disconnected.  This was voltage
> induced in the phone cables from whatever power cable the bundle was
> lashed to.

:-) Well we thought that Ethernet protective devices would mitigate
such problems, and maybe they do mitigate them after all (i.e. I would
get toasted switches every day and not twice a year).

-- 
Victor Sudakov,  VAS4-RIPE, VAS47-RIPN
sip:sudakov at sibptus.tomsk.ru