NETGEAR CG814M manual Ethernet Cabling, Uplink Switches and Crossover Cables

Reference Manual for the Model CG814M Wireless Cable Modem Gateway

Note: The available channels supported by the wireless products in various countries are different.

The preferred channel separation between the channels in neighboring wireless networks is 25 MHz (5 channels). This means that you can apply up to three different channels within your wireless network. There are only 11 usable wireless channels in the United States. It is recommended that you start using channel 1 and grow to use channel 6, and 11 when necessary, as these three channels do not overlap.

Ethernet Cabling

Although Ethernet networks originally used thick or thin coaxial cable, most installations currently use unshielded twisted pair (UTP) cabling. The UTP cable contains eight conductors, arranged in four twisted pairs, and terminated with an RJ45 type connector. A normal "straight-through" UTP Ethernet cable follows the EIA568B standard wiring as described in Table 6-1.

Table 6-1.		UTP Ethernet cable wiring, straight-through
Pin	Wire color		Signal
1	Orange/White		Transmit (Tx) +
2	Orange		Transmit (Tx) -
3	Green/White		Receive (Rx) +
4	Blue
5	Blue/White
6	Green		Receive (Rx) -
7	Brown/White
8	Brown

Uplink Switches and Crossover Cables

In the wiring table, the concept of transmit and receive are from the perspective of the PC. For example, the PC transmits on pins 1 and 2. At the hub, the perspective is reversed, and the hub receives on pins 1 and 2. When connecting a PC to a PC, or a hub port to another hub port, the transmit pair must be exchanged with the receive pair. This exchange is done by one of two mechanisms. Most hubs provide an Uplink switch which will exchange the pairs on one port, allowing that port to be connected to another hub using a normal Ethernet cable. The second method is to use a crossover cable, which is a special cable in which the transmit and receive pairs

Networks, Routing, and Firewall Basics B-15