Problems connecting 10BaseT to 10Base2

Problems connecting 10BaseT to 10Base2

Post by Randall Asa » Tue, 09 Mar 1999 04:00:00

: Speculation; for utp, the uplink port requires the crossover cable which
: essentially acts as a null modem.  Is there something similar in concept to
: this at work with the bnc uplink??  There are no configuration switches on
: the D-Link DE-809TC.  Email to D-link has gone unanswered for several days
: now.

The BNC doesn't operate as a "uplink" as the UTP does. It usually is just
another port on the hub.  UTP uses four conductors.  A pair to transmit
and a pair to receive.  To attach workstations without a hub, the pairs
must be switched at one end, or "crossed-over."  The purpose of the
uplink port is to attach two hubs together *WITHOUT* haveing to use
acrossover cable.  Most hubs have a switch so that one of the UTP ports
can be used as wither a regular port or to connect to another hub.

BNC (10b2) uses just two conductors. It is a bus type topology so each
workstation attaches by "tapping in" to the bus.  That's the purpose of
the t-connector.  There should be a t-connector on every device.  Then
attach a coax between every t-connector.  Finally put a terminator on the
t-connector of the two end devices.  So if you only have the hub and the
workstation, it should go like this: terminator on T, wire from T to T,
terminator on T.  If you want more info, head to the bookstore.  I started
with "Networking for Dummies" because it had some pretty pictures.

: Can the 'uplink' port simply connect to the bnc network.  Is this strictly
: intended as a backbone to connect to other hubs??

Some hubs I've seen had a switch or switches to activate/deactivate the
UTP uplink and/or the BNC port.  Some hubs don't allow the simultaneous
use of the BNC and the uplink (e.g.: the UTP port must be set to normal

: I understand I should convert the whole thing to utp.  However, this house was
: wired when built, and I would really like to use the existing (hidden) network
: cable.

No, not really.  The kind of wiring you use depends on the situation.  UTP
is not shielded.  Coax is.  If you have EMF interference, you'd have to
go Sheilded Twisted pair.  More expense. My house is wired 10b2 because I
have several computers but they are all in different rooms.  So 10bT would
mean that some of the wires would run parallel to each other.  That means
that I've have to run more wire,increasing my cost.  If you can get your
network to work, then i'd suggest you leave it alone.

Just my two cents,
Randall T. Asato
Student Lab Manager
Business Education Division
Leeward Community College, University of Hawaii

- If the universe is expanding, why can't I find a parking space?


1. "Newbie" problem connecting 10BaseT & 10Base2 networks through Hub


I'm runing into a strange problem that I suspect is either obvious
or a newbie type mistake.  I've got 2 networks running MS Windows
for Workgroups 3.11.  The first is made up of various clones
using 3Com 3C503 cards & thin ethernet.  The second are "older"
IBM PS/2's (486 equivalents) using 3Com Etherlink/MC cards
and 10BaseT ethernet.

The problem is that each network works fine independently,
but I've tried 3 different 10BaseT hubs with BNC output
connectors (2 different brands, LanPRO and the other is "generic")
and when I connect the thin ethernet to the hub, most of the time
the machines on one network don't see the others, or when they
do, accessing them generates frequent errors.  Probably significant
is that I've noticed that whenever I tell a machine to access
something on the other network, every access to the network also
results in the hub's COLLISION light to flash.

Things I have checked: thin ethernet is terminated (total length
200-300 ft).  When I put one of the clones on the 10BaseT netowrk
with a different ISA card with 10BaseT, it works fine & reliably
on that network, but then has problems getting back to the thin
ethernet network.

So, is there something I'm missing here ?  Could I have gotten
3 different bad hubs ?  Is there something in the WFW configuration
that I need to check ?

I'm stumped, so any help would be appreciated.

-brad albom
Software Engineering Solutions, Inc
2685 Marine Way, Suite 1215, Mountain View, CA 94043

phone: (415) 969-0141
alt  : (707) 552-5248

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