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Hardware Installation and Network TopologyCHAPTER 1
Straight-through vs. crossover cables
Ports on the switch are wired MDI so you can use a straight-through
cable when connecting to a Fast Ethernet repeating hub port, which is
usually wired MDI-X. For direct connection to another MDI port
(workstation, server, or another switch), you must use a crossover
cable. The pinouts of MDI and MDI-X ports are shown below.
Connector pinouts
Switch or NIC RJ-45 (MDI) Hub RJ-45 (MDI-X)
1TX+ 1RX+
2 TX- 2 RX-
3 RX+ 3 TX+
4 Unused 4 Unused
5 Unused 5 Unused
6 RX- 6 TX-
7 Unused 7 Unused
8 Unused 8 Unused
Determining which cable to use
Different switch and repeater manufacturers implement their port
configurations differently. The following guidelines are based on the
Intel Express 100BASE-TX Switching Hub (switch), the Intel Express
100BASE-TX Stackable Hub (repeater) and the EtherExpress™
family of adapters (server or workstation). These apply to the majority
of switches and hubs:
For this connection Use this cable
Switch to repeater Straight-through
Switch to server or workstation Crossover
Switch to switch Crossover
Repeater to server or workstation Straight-through
NOTE
When making your own
cables, wires 1 and 2
must be a twisted pair
and 3 and 6 must be a
twisted pair.