Look down a few posts in this forum for "Network Segment lengths" it has some good info in it. Also, FWIW here is a quote from a Net+ newsgroup that is having the same discussionMC
<begin quote from alt.certification,network-plus>
Ok. imagine five 100-meter lengths of cat5 ethernet cable, with RJ45
jacks on each end. You have an office buidling 500 meters across and
have three computers you'd like to put on a single network. One
computer is on each end of the building, with the third computer smack
in the middle. The 5 ethernet cables represent the "5" in the
5-4-3...segments on the network.
You hook up one end of cable to a computer on one end of the building,
but of course it won't reach either computer...it's 400 and 150 meters
too short, respectively. So you add a repeater, which boosts the
signal. This almost reaches the middle computer, but short by 50
meters. You add a SECOND repeater, and you reach the computer in the
middle. You add 2 more repeaters and then you can reach the other
end. The repeaters represent the "4" in the 5-4-3...maximum number of
repeaters. An active hub (meaning it has a power plug) is considered
a "multi-port repeater".
<computer1>---repeater1---repeater2--<computer2>---repeater3----repeater4----<computer3>
So all three computers are hooked up. Now Joe Smith in accounting
gets an idea. He adds his computer between the 1st and 2nd repeaters
and never tells the network administrator. This is not allowed and
will cause problems on the network because of the "3"...a maximum of 3
segments with computers on the network (his computer would populate
*4* segments, since its between repeaters 1 and 2...placing a computer
between repeaters 3 and 4 would do the same thing)
So theres the 5-4-3 rule. Max 5 segments, 4 repeaters, 3 segments
populated.
)