Thin Ethernet (10base2)
||I have seen now so many
messages on the News-Groups, and also received so many
messages on this topic, that I am putting it up now like
on a 10base2 coax network-cable,
there MUST be a 50 Ohm terminator
on each end : One
terminator MUST be grounded, the other NOT !
(And it does NOT work to plug the
BNC-connector of the coax-cable directly onto the
BNC-connector of the NIC without T-connector !)
The dangerous issue: if you put on TWO not-grounded
if you ground BOTH terminators, the network does NOT fail
completely, but I can guarantee you problems: slow,
unreliable, errors during data-transfer !
Thin Ethernet (10base2), sometime also called "Cheapernet", is based on using a coax-cable, which is specified as RG58
(please, do NOT use other type of coax-cable, it has other
electrical properties and will not work properly) and which runs
from system to system.
The cable is connected via BNC-T-connectors
to the network card installed in the PC.
The T-connector must be put on the
BNC-connector of the network card !
(if you have a Combo / Multi-Connector
Board, check, if you need to
select the BNC-port !)
||It is NOT allowed to put
in any extension/cable between the
T-connector and the BNC-connector on the network card !
If you do that, your network will either NOT work or
working slow or sometimes failing !
||The T-connector is
put directly on the
BNC-connector of the
||If one of the systems
located away from the
cable, you CANNOT use
a drop-cable from the
t-connector to the
BNC of the Network
Card (NIC) !
It either does NOT work
or works unreliable /
||Run the cable to the
system and then
run it back
(watch out NOT
to exceed the
cable-length ) !
||Put in a separate
which allows to connect the
remote located system on its
own segment, which need
to have its own terminators.
So, a more realistic view on an installation is:
The cable swings from system to system (it is NOT allowed to
put in "junctions" , to connect for example 3 PC's in a
At the end of the cable, the coax-cable MUST be terminated, using
a BNC 50 ohm terminator.
||Let me repeat that:
(and not 75 or any other value ! )
There are 2 different type of terminators:
The original Thin-Ethernet specifications state, that the
cable has to be terminated at one end with an "open
terminator" and on the other side with a "grounded
terminator", a wire or small chain, which has to be
connected to a metal-part on the back of the PC to get a
I know, that a lot of documentation shows only 2 "open"
terminators,and that "grounded" terminators are
sometimes difficult to find. One small networks, it even works
"somehow", but not reliable and not at top-speed.
I have been asked several times:
"How do I recognize an OPEN and a GROUNDED Terminator ?"
||No wire or chain : open
||A wire or chain: a Grounded
Don't forget to connect it to a metal part of the
otherwise it is NOT grounded !
The need for the terminators require to shutdown the complete
network, when having to add a new system to the network (see Twisted Pair versus Coax: Reliability /
each connection to an Thin-Ethernet RG-58 cable is called a
"node", which can be a system like a
PC, a UNIX-workstation or a Fileserver, but also anything else
connecting via a BNC-connector counts a a node (network printers,
- maximum 30 nodes on one Thin-Ethernet segment
- minimum 0.5 meter distance between nodes
- maximum total cable-length of 185 meter
If more than 30 nodes need to be connected or if the total
cable-length needs to be longer
than 185 meters, a repeater is the
For each cable-segment, you need to be within the
10base2 limitation (max. 185 meter, 30 nodes),
but this box called "Repeater"
connects now the 2 (or even more) segments (some
Multi-port repeaters can connect 4 or even 8 cables),
which in view of the users extends the cable-length
beyond the 185 meters. More than 1 repeater can be used in a
network, but there are limits (see Large Networks: 5-4-3 Rule). On very large networks, it will be required to
install Switches to optimize network
||You want a "healthy" network ?
you need one "open" terminator at one end of
and one "grounded" terminator at the other end
of the Thin Ethernet cable !
Without proper "termination", the network may
it may work, but then unreliable or slow.
This need for a GROUNDED terminator is not
mentioned often in other documentation,
but I am sure about this due to my own experience and also due to
the feedback, which
I am getting back from my visitors, example (received
"I found your emphasis on grounding one end of thin-net
coax extremely helpful.
I had a working network, except for one machine. We had
I finally got the one machine on the net after I grounded one end
of the cable.
I think maybe the slow-downs will stop also, we will see.
Note: As I remember, I have seen nothing mentioned about
grounding of the thin-net cable
any where else. "