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Nemesis · 20-02-2013, 16:43

Cat 5 cable is typically unshielded twisted pair, containing four twisted wire pairs. Fast Ethernet (100Base-T) and 10Base-T use only two of these pairs, leaving two pairs unused. Gigabit Ethernet (1000Base-T) uses all four pairs.

Similar to full-duplex Fast Ethernet, 1000Base-T transmits and receives simultaneously. The difference is that 1000Base-T uses four transmit/receive pairs, each pair operating at 250M bit/sec.

In some respects, running Gigabit Ethernet on Cat 5 cabling is easier than wiring for 10/100M bit/sec Ethernet. The 1000Base-T specification provides for the automatic negotiation of link characteristics, including automatic crossed cable correction. Automatic negotiation enables successful cable connections between 1000Base-T network interface cards (NIC), hubs, switches or other devices that may operate at half-duplex when the ports are initialized.

The intelligence built into many 1000Base-T interfaces can also negotiate the proper speed to use if attached to a 100M bit/sec port by mistake. The gigabit port will operate at the highest common denominator speed thereby preventing any damage to either device interface. Using 1000Base-T NICs on servers and associated switching devices in the network allows a company to continue using its Cat 5 cable infrastructure, while providing an effective high-speed connection.

Basically check your connections, and buy a cable tester.

20-02-2013, 16:43	#31
Nemesis Inactive Join Date: Jun 2003 Location: Surrey Age: 58 Services: Virgin stuff Posts: 6,407	Re: UTP Cable Wiring Nightmare Cat 5 cable is typically unshielded twisted pair, containing four twisted wire pairs. Fast Ethernet (100Base-T) and 10Base-T use only two of these pairs, leaving two pairs unused. Gigabit Ethernet (1000Base-T) uses all four pairs. Similar to full-duplex Fast Ethernet, 1000Base-T transmits and receives simultaneously. The difference is that 1000Base-T uses four transmit/receive pairs, each pair operating at 250M bit/sec. In some respects, running Gigabit Ethernet on Cat 5 cabling is easier than wiring for 10/100M bit/sec Ethernet. The 1000Base-T specification provides for the automatic negotiation of link characteristics, including automatic crossed cable correction. Automatic negotiation enables successful cable connections between 1000Base-T network interface cards (NIC), hubs, switches or other devices that may operate at half-duplex when the ports are initialized. The intelligence built into many 1000Base-T interfaces can also negotiate the proper speed to use if attached to a 100M bit/sec port by mistake. The gigabit port will operate at the highest common denominator speed thereby preventing any damage to either device interface. Using 1000Base-T NICs on servers and associated switching devices in the network allows a company to continue using its Cat 5 cable infrastructure, while providing an effective high-speed connection. Basically check your connections, and buy a cable tester.