27 Mar
2001
27 Mar
'01
9:16 p.m.
On Mar 28, 2:47, Iggy Drougge wrote:
This weekend, along with a batch of PS/2s, I received
a 3Com 3c588 1988
vintage MultiConnect Repeater. It's a 19" case with space for sixteen
cards.
Mine features one card indicating power with a green
LED as well as a
DB-9
female connector, then fourteen cards equipped with a
BNC connector, an
activity led, one partition LED and a partition/reset switch each.
Whenever a card is connected to a 10b2 network, the partition light
(which
otherwise emits a steady red light) begins to flicker.
Upon flicking the
switch into reset mode, the partition light goes out. The network works
fine
as long as there is no partitioning. I suppose its
purpose is to not leak
traffic between several networks.
Not quite. "Partitioning" is network jargon for disconnecting a port or
segment. If there's no terminator, the transceiver will behave as though
continually detecting collisions, and the repeater will automatically
disconnect ("partition") that transceiver from the rest. The red LED
lights up to tell you it has done so. It won't self-reset because if it
really were connected to a faulty network segment, it might end up going in
and out of operation.
What is the purpose of the DB-9 connector?
I'm not familiar with this particular repeater, but I imagine it's a serial
port for management and setup. Modern 3Com equipment has a serial port
wired to the same (non)standard as PC 9-pin ports, but that one may not be
wired in the normal way. It may also do auto-baud-rate detection, and it
probably won't emit anything until it receives a couple of carriage
returns. My old SynOptics 2813 hubs have a DA9 as well, and it's some odd
connection for a modem (they also have a DB25 whichj is a normal serial
port).
I'd pull the card and see if anything on it gives you any clues.
Could this repeater slow a network down?
Unlikely. You can get different cards for those repeaters -- 10baseT,
10base2, 10base5/AUI, and the 10baseT cards have 3 ports each. 3Com
wouldn't have done that if it were going to significantly impact bandwidth.
It's basically just a buffer; it doesn't process the data passing through
like a switch does. Any intelligence in it is just for monitoring and
setup (partitioning, etc).
Another thing you could try is snooping on the network packets (if you have
snoop, tcpdump, or similar) to see if the repeater emits any packets when
it first powers up. It might be trying to BOOTP to get an IP address, and
if you give it one, you can probably telnet to it and look at the setup.
It probably needs a password, though.
What does partitioning actually entail?
See above. Some more modern 3Com hubs also have the capability to split
the unit into segments (eg, the SuperStack II PS 40 hubs and others can
have 4 segments) but assigning ports to different segments isn't usually
called partitioning.
--
Pete Peter Turnbull
Network Manager
Dept. of Computer Science
University of York