[Asterisk-Users] OT: VoIP over bonded link

[Rich Adamson]

> > It's stupid. Don't ever connect 2 different building with copper.
> > Just wait until you get some kind of lightening hit or electrical
> > fault, but make sure you are no where near it. Use fibre.
> 
> That's a great rule of thumb, but the reality isn't quite so black and white.
> 
> A direct lightning strike is not going to draw *any* significant current 
> through the ethernet cable, as the moment you try to pull significant 
> current, those cables will either open up or vaporize due to IR losses in 
> such small gage wire.  You'll have far more current draw through the (I'm 
> assuming) metal conduit, which is already grounded.

The above is really not true with many production switches. Any form of static
electricity (regardless of whether its sourced from lightning for people) can
and have been known to blow the ethernet interface IC inside the switch.
(I can have some of our customers ship a boat load of those to you if you
want. You pay shipping. ;)

Cabletron and SMC switches seem to be the worst, and SMC manufacturers a lot
of entry level workgroup switches for other well known companies.

> Yes, you may introduce grounding loops and these will cause other (sometimes 
> significant) issues but they have all been solved before.  The best solution 
> is to simply take a pair of media converters with a fiber patch cable between 
> them, space them out adequately and hope for the best.  You're already going 
> to have a conduction path through the power supplies of the media converters 
> but with an isolation transformer and appropriate surge arrestors it's about 
> as best as you are going to be able to do.

The above concern have been a major issue with telephone equipment (eg, central 
offices) and the telco's spend a significant amount of money burying very long 
rods in the ground and interconnectng them with the CO hardware using cables 
that are larger then 1/4" in diameter (don't remember the guage anymore).
Every row of racks include the heavy ground cabling, and rack paint (etc)
is often times scrapped off between racks to ensure a solid ground.
They use special test equipment to actually measure the implementation.

Historically, Florida locations have very poor grounding which is known to
cause telco's issues for sure.