[NCLUG] 100 Mbit cabling

[Michael Dwyer]

dherr at frii.com wrote:
> I've heard two different answers to this question, and I'd like
> to know the correct answer before I start pulling cable in my house.
> For a 100 Mbit ethernet connection, are all 8 wires needed, or just
> the same 4 wires that are used for 10-BaseT?  This will determine
> how many 8-wire cables I need to bring to a given location.

For MOST 100MBit signals, (100TX?) you need the usual tx and rx pairs. 
So, four wires.  But the question you /asked/ was about 100MBit 
connections in general...  In which case, you DO need all eight wires. 
I believe that the 100VG standard uses all eight wires.  ATM appears to 
depend on four wires, but different pairs.  Ditto for Token Ring.

I suggest that you pull extra cable instead of trying to split them.  It 
works, but it is a Bad Thing in the long run.

By the way, the wiring standards (ANSI/TIA/EIA-568) suggest:

   A minimum of two telecommunications outlets shall be provided to
   each work area. The two outlets shall be configured as follows:
     1. One connector shall be supported by a 4-pair 100d UTP
        cable, Category 3 or higher
     2. The other shall be supported by a minimum of one of
        the following:
        a. 4-pair 100 dUTP cable (Category 5 recommended)
        b. 2-pair 150dSTP cable
        c. 2-fiber, 62.5/125 um optical fiber cable

In other words, every work area should probably have a CAT3 phone line, 
and the other should be a CAT5 wire.  You should only split the wires 
when, two years down the road, you discovered that you didn't pull 
enough cable. :)