Twisted Pair Ethernet (10baseT/UTP)

by Johannes Helmig [Published on 24 March 2001 / Last Updated on 24 March 2001]

Note: most of the rules for 10BaseT are also valid for Twisted Pair Ethernet (100baseTX/100BaseT4)

Twisted Pair Ethernet (10baseT), sometime also called "UTP" from "Unshielded Twisted Pair", is based on using a cable similar to phone-wiring. The cable is connected via an RJ-45 connectors to the network card installed in the PC.

If you have a Combo / Multi-Connector network Board, check whether you need to configure the RJ45 plug (it is not always done automatically ! ).

These Twisted Pair cables connect now each PC to the "hub":

which is amplifying and distributing the signal to other connected systems.

Hubs are available in different configuration, with 4, 8, 12, 15 or 24 RJ-45 connections (and most models offer also a BNC-connector for connection of a 10base2 Thin Ethernet cable).
You can plug in the RJ45-connector into a hub while the network is running on the other connected systems, allowing to move / add systems without having to shutdown the network (see : Twisted Pair versus Coax: Reliability / Advantages )

When the network grows, you may need a second hub:

Warning: there are different cable to connect the hubs !
If the hub has only regular connectors, the cable MUST be a cross-cable !

However, some hubs offer special connectors for use of 'Standard' cables
to connect between hubs (that depends on the hub, check the hub's manual)
or a switch, able to select : 'workstation' or ' hub' connection.

Have a look at the back of your hub:

Usually the ports are numbered, and the highest port has a switch labeled"
"Uplink" or something like "MDI/X" in the picture above, allowing you
to configure the port for connection to another hub using a regular cable.
Note: if you use a regular cable to connect 2 hubs, ONLY one hub must
configure the port for this purpose, on the other hub you MUST connect
the cable to a regular port :

For even larger networks, more hubs are required:

Again, watch out for the type of cable required to connect the hubs.

Often , you find a combination of Twisted-Pair and Thin Ethernet (10base2) cabling:

A Thin-Ethernet cable is used to connect the hubs, such a cable is then often called "the backbone", because it carries all the traffic to/from the server.
Warning: the Thin Ethernet (10base2) backbone MUST follow the 10base2 specifications (length, terminators,...).
Warning: a network cannot grow unlimited in the number of hubs and repeaters
(see: Large Networks: 5-4-3 Rule) and on very large network configurations, it may be required to install Switches to optimize the network utilisation.

When connecting just 2 PC's together, there is a possibility to do it without a hub:

BUT: it is now a different type of cable: it is a "crossed" 10baseT cable !
Using a 'regular' cable (which is supposed to be used for connection to a hub) is a common
cause of error, such a 'regular' or 'straight' 10baseT cable does NOT work in such a configuration
without a hub.

I strongly suggest to purchase a cable, but if you think you can make it properly, here is the layout
of such a crossed 10baseT-cable
(i.e 10 MHz, this cable is NOT for 100baseT/100Mhz, for that look at Twisted Pair Ethernet (100baseTX/100BaseT4))

See Also

The Author — Johannes Helmig

Dr.Johannes Helmig is working as Director, Technical Knowledge Management in the Belgium office of Gerber Technology where he is involved in Customer Service and internal training, with special interest in Networking.


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