Cable Quality - NETGEAR FVM318 Reference Manual

Reference Manual for the Model FVM318 Cable/DSL ProSafe Wireless VPN Security Firewall
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 are exchanged at one of the
two cable connectors. Crossover cables are often unmarked as such, and must be identified by
comparing the two connectors. Since the cable connectors are clear plastic, it is easy to place them
side by side and view the order of the wire colors on each. On a straight-through cable, the color
order will be the same on both connectors. On a crossover cable, the orange and blue pairs will be
exchanged from one connector to the other.
The FVM318 firewall incorporates Auto Uplink TM technology (also called MDI/MDIX). Each
LOCAL Ethernet port will automatically sense whether the Ethernet cable plugged into the port
should have a normal connection (e.g. connecting to a PC) or an uplink connection (e.g.
connecting to a router, switch, or hub). That port will then configure itself to the correct
configuration. This feature also eliminates the need to worry about crossover cables, as Auto
Uplink TM will accommodate either type of cable to make the right connection.

Cable Quality

A twisted pair Ethernet network operating at 10 Mbits/second (10BASE-T) will often tolerate low
quality cables, but at 100 Mbits/second (10BASE-Tx) the cable must be rated as Category 5, or
Cat 5 or Cat V, by the Electronic Industry Association (EIA). This rating will be printed on the
cable jacket. A Category 5 cable will meet specified requirements regarding loss and crosstalk. In
addition, there are restrictions on maximum cable length for both 10 and 100 Mbits/second
networks.
B-20 Network, Routing, Firewall, and Wireless Basics