Unshielded
Twisted Pair (UTP) is a cable that has four pairs
of wires twisted inside it to eliminate electrical
interference. UTP cables are connected using RJ-45
connectors that have eight connector pins. The data
equipment that is used for internetworking is classified
as Data Terminal Equipment (DTE e.g. router interfaces)
and Data Communication Equipment (DCE e.g. A WAN
connects DTEs through DCE network).
UTP cables are used in many configurations and
for different purposes, to form an internetwork
including:
Straight-through
Crossover
Rollover
Applications of UTP include:
Serial transmission
Integrated Service Digital
Network (ISDN) connections
Console connections
Modular and fixed interfaces
These configurations and applications are discussed
below.
Straight-Through Cable
A straight-through cable is the standard network
cable connection and is used to connect the source
and destination computers through an internetworking
device. Specifically, you can use it to connect
a host to a hub or switch
Crossover Cable
In a crossover cable, the standard RJ-45 cable
between the source and destination computers
is cross-connected. A crossover cable can be
used to connect:
Two computers
Two hubs
A hub to a switch
A cable modem to a router
Two router interfaces
Rollover Cable
These Cisco proprietary cables used to connect
to a router or switch console port. In a rollover
cable (8 pins), RJ-45 connectors are usually
present at each ends and are used to connect
router and computer ports. Pin 1 on one end of
cable connects to Pin 8 at the other end of the
cable, similarly, Pin 2 connects Pin 7, and so
on.
Serial Transmission
All WANs use serial transmission, which can pass
one bit at a time over a single channel. Cisco
provides a 60-pin serial connector for one end
of the cable while other end of the cable may
be EIA/TIA-232, V.35, EIA/TIA-449, X.21 or others;
ISDN Connections
ISDN refers to a collection of standards that define
a digital architecture that can carry integrated
voice and data, using the public-switched network.
ISDN BRI (Basic Rate Interface) is a two 64 kbps
Bearer channels (2B) plus one 16 kbps Data channel
(D) service. ISDN BRI terminates at the customer
premise with the U interface.
Console Connections
A console is a type of DTE through which commands
are entered into the host device. Most Cisco
devices support the RJ-45 console connection.
A rollover cable with an RJ-45 connector is used
to connect the PC or terminal to the console
port of the Cisco device.
Modular and Fixed Interfaces
Unlike a fixed interface router, a modular interface
router allows you to add new interface cards
without buying a new router.
