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Token Ring: Cross-Connect possible?

Posted on 2000-03-31
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Last Modified: 2010-05-18
Two PCs with Ethernet cards may be connected thru a "cross connect cable", i.e. a patch cable having the send and receive wires reversed.

Is this also possible for PCs with Token Ring cards?
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Question by:Stefan_P
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by:Otta
ID: 2673838
No.
The "token" is passed to the next computer in the "ring", and the ring is "closed" (that's why it is called a "ring").

In general:

A -> B -> C -> ... -> A

The ring can be small:

  A -> B -> A

but this is not a "cross-over";
it's only a _small_ ring.
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by:SysExpert
ID: 2673882
I agree.
I beleive you have to have an MAU in any case..
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by:jgarr
ID: 2676144
Token-Ring requires a MAU or CAU to connect stations.
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by:tonnybrandt
ID: 2676747
All here are right.
Did try it once, but had to get a mau to get the job done.
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sime788 earned 100 total points
ID: 2680200
Token ring requires a MAU (Multi Station Access Unit Or A CAU (Controled Access Unit) with LAM(S)Lobe Attachment Modules.

Token Ring is a LOGICAL ring But wired as a PHYSICAL star.

A MAU or MASU's are wiring concentrators and come in 2 flavours Active and Passive, with active the more common (an active MAU boosts the signal and allows more stations to attach to a single ring)

When you plug a lobe attachment cable from your Token Ring card to the MAU and boot the device a number of things happen. The NIC does a self test to check it's OK once complete it generates a "Phantom current" (Phantom because it uses the same wires as  data normally uses) usually + 5V and chucks it down the lobe cable at the MAU. The current forces a valve open in the MAU. In the open state data can flow from the MAU down the Lobe cable into the NIC (1 bit at a time) and back up the lobe cable and onto the next port. When you power off your device the Phantom current drops and the valve in the MAU slams shut any data passing through the MAU now bypasses the port and goes on to the next open port.

The conceptual ring is created by putting one end of a lobe cable into RI (Ring in) and the other end into RO (Ring out) although it is not necessary.
These RI / RO ports also allow you to cascade MAUs where RO of 1 MAU feeds to RI of the next MAU and so on with the RO of the final MAU feeding back to the RI of the First MAU.

Now if you go plugging a Token ring card directly into another Token Ring Card (as you can with Ethernet) at best it won't work at worst there will be a puff of smoke and a bang... +5 volts directly into a NIC is not a good idea.

If you want to know more the best book around is Network Protocols by Mathew Naugle  McGraw Hill ISBN 0-07-046603-3

Simply put don't do it or you'll likley break something :-)

Hope this helps

Sime
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by:Stefan_P
ID: 2680973
I'm not sure about those 5 volts being a danger for the NIC. I once connected a token ring card to a telephone line by accident (well, they both have RJ45 plugs...). The 40 volts from the telephone line didn't break the NIC.

Nice background info though. Thanks!
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by:sime788
ID: 2681286
No problem, glad to be of help

Later

Sime
 
:-)
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