Communication Equipment
connect into data communication equipment (DCE), for example, a channel
service unit/data service unit (CSU/DSU). The CSU/DSU then plugs into a
demarcation location (demarc) and is the service provider's last responsibil-
ity. Most of the time, the demarc is a jack that has an RJ-45 female connector
located close to your equipment. You may have heard of demarcs if you've
ever had the glorious experience of reporting a problem to your service
provider--they'll always tell you it tests fine up to the demarc, and that the
problem must be the CPE, or customer premise equipment. In other words,
your responsibility, not theirs.
through the provider's wiring and switches, all the way to the CSU/DSU at
the other end. The network's DCE device provides clocking to the DTE-
connected interface (the router's serial interface).
ular. The fixed routers, such as the 2500 series, have set interfaces that can't
be changed. The 2501 router has two serial connections and one 10BaseT
AUI interface. If you need to add a third serial interface, then you need to buy
a new router--ouch! However, the 1600, 1700, 2600, 3600, and higher
routers have modular interfaces that allow you to buy what you need now
and add almost any type of interface you may need later. The 1600 and 1700
are limited and have both fixed and modular ports, but the 2600 and up pro-
vide many serials, FastEthernet, and even voice-module availability--now
we're talking!