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Thread ID: 43453 2004-03-15 07:41:00 Ethernet Hubs...Uplink port??? MrBeef (342) Press F1
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222687 2004-03-15 07:41:00 Hi there, ive used a few hubs in my time and i have always been curious, but not curious enough to look it up about what an Uplink port is??

What be this, what uses it, how can it be utilised?
MrBeef (342)
222688 2004-03-15 07:44:00 MrBeef,

With my e-net switches I use them for daisy-chaining... ie linking multiple switches together....

Cheers, Babe.
Babe Ruth (416)
222689 2004-03-15 08:14:00 Oh i see, makes sense, Uplink it to another hub..perhaps our school switches have the same, most have a looksie MrBeef (342)
222690 2004-03-15 08:24:00 to hook a hub to a hub you would need a crossover cable just like when you hook a computer to a computer with out a hub.

the uplink port has the wireing set so you hook a uplink port on one hub to a normal port of the other hub.

if you try and hook an uplink port to another uplink port you will need a crossover cable.....

hope that makes sence.
robsonde (120)
222691 2004-03-15 11:15:00 Also handy for pluging your modem/router into, no crossover needed if it says it is auto sensing mbx (or something similar for the later IIRC)

WAN -----> Modem/router/gateway -----> uplink port on hub/switch =====>> Lan.

Cheers Murray P
Murray P (44)
222692 2004-03-15 15:08:00 > Also handy for pluging your modem/router into, no
> crossover needed if it says it is auto sensing mbx
> (or something similar for the later IIRC)

Mine doesn't need one. It has 4 ports 10/100. All auto sensing so it detects the cable type as well as the speed. Can use cross overs or straights.
Big John (551)
222693 2004-03-16 01:12:00 But no-one has said what it does and why it is called an uplink port. ;-)

An xBaseT transceiver --- Ethernet using twisted pair cable --- uses one pair of wires for transmit and the other pair for receive. If you connect two tranceivers together with Tx to Tx and Rx to Rx, you don't get any communications. This is Not a Good Thing.

A hub has a clever chip or set of chips which receives from the transmit wires from a port connected to one computer, and copies the packets out to the receive wires of all the other computer ports on the hub. So each computer is connected Tx- Rx Rx-Tx to the hub. And it all works. :O

Now you want to expand your network. You haven't got any ports left on youir hub, except the one marked "Uplink". (Or you have used even that one, because there is a switch beside it marked "Normal/Uplink" or just a switch with "X" on one side. ) You can't use a straight through cable from a normal port to a normal port on the other hub, because that would connect Tx-Tx and Rx-RX. You could use a crossover cable, but anyone who has had anything to do with computer cables hates crossover cables. (Because they are different. Labels fall off, and they get installed by mistake. :_| )

So nice manufacturers give you a port which is crossed over so it will connect Tx-Rx and Rx-Tx on an "ordinary" port on another hub. The nicest ones give you a port which can be switched between straight or crossed, because that doesn't "waste" a port if you don't need expansion. Some older hubs use a BNC connector which can connect into a 10Base2 network. That can connect straight to a BNC on another hub because 10Base2 doesn't need swapping (there's only the inner and the outer of the coax. :D).

You have probably noticed, if you have followed this carefully, that all the ports except the uplink one are actually crossed over. :D
Graham L (2)
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