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I have added several new computers to a home network and I run out of free ports a gigabit-in switch... Two of the connected devices are printers and run just ocasinally. I would like to have all devices connected without running a second switch or buying a bigger one. My ideas to stuff two devices in one port are:

1) since FastEthernet only uses two pairs and the cables and ports in switch have four pairs it should be possible to connect two pairs of each printer to four pair of the switch. in that case: how to connect it everything?

2) Connect everything 1:1 and rely on CSMA/CD to resolve any collisions (there should be only few because the cable is mostly idle...

Any thoughts/Ideas/other solutions?

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Even if you did splice the wire into two, how would you make the switch recognize the printers as separate entities? A switch is designed to address one other device per port, whether it's a printer, a computer, or another switch. The problem here is not network collisions; the switch simply can't address two devices on the same port and magically know which wires are TX/RX for either device. If you have a magical switch that can, let me know so I can buy a few ;). –  squircle Jul 19 '10 at 14:47

2 Answers 2

Connect all low-bandwidth devices to a low-cost network hub and the extension port of the hub connect to the switch.

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I have a spare switch, which is likely to be the final solution, I was just interested how to use the unused pairs in cables/switch and the collision detection ethernet has - after all it was supposed to have a shared medium... –  Lukas Jul 19 '10 at 14:59

Technically, the 802.3 specification indicates that communication IS possible, since it is only concerned with MAC addresses (Layer 2). As long as you maintain the wire twist and re-sheathe the cable some how, you can wire the pairs to 1&3 and 2&6 on a standard RJ-45 (mindful of crosstalk), they will communicate. A hub only regenerates the signal, regurgitating the data it receives out all of its ports. Just make sure to use different IP addresses and I think it would work.

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You run a high risk of collisions if you try to communicate simultaneously. If the port can be configured as full duplex, try it! –  Daniel Barlow Apr 29 at 22:27

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