Do I have to connect all 8 wires of a LAN cable ?

If you are using 100Base-T4 standards - that is you want to use cat 3, 4 or 5 cables ALL 4 PAIRS (8 wires) ARE REQUIRED. If you are using 100Base-TX (category 5 or 5e cables only) or 10Base-T the wires numbered 4 and 5 (one pair) and 7 and 8 (another pair) are not used in normal LAN operation but should still be connected since some equipment may use them for special purposes (we use them for power-over-ethernet in certain applications). They can be used for other functions e.g. telephony see above.

Beware: You are taking a RISK that in the future some genius may invent a fantastic application for one or more of these pairs and you may have to re-wire. Whether you consider this a high or low risk is a personal decision.

What is category 5 (or Category 5e or Category 6) cabling

Category 5 UTP (Unshielded Twisted Pair) cable is defined by the EIA/TIA for use with 10 and 100 MB LANs (10baseT and 100baseT) as specification number EIA/TIA-568A. Category 5e is a slightly improved specification published as EIA/TIA-568A-A-5 . Category 6 is defined by EIA/TAI-568-B.2-1.

Hub vs Switch

The price difference between a Switch and a Hub is almost vanishly small these days. Unless budget really is a key issue we would suggest a Switch. They come in all kinds of sizes 4, 5, 8, 16 and 24 ports. some have the ports at the back and leds at the front, others put both at the front.

RJ45 and LEDS at front

RJ45 at Rear LEDS at front

The general specification - irrespective of whether its a switch or hub - is:

1. Minimum number of ports equal to the most systems you can think of connecting plus some (say 2) ('cos you are going to change your mind!)
2. 10/100 Mbit/s auto sensing
3. LINK LED for each port
4. 10/100 LED for each port

They typically come with lots of other features e.g. Full/Half Duplex, managed or unmanaged - your budget will figure out what else you want or can afford.

RJ45 Male Connector Pin Numbering

RJ45 Male Connector