Comms Testlab Wiring FAQ

RJ45 plug pin guide

EIA/TIA 568A RJ45 plug pinout
Pin # Color Pair Signal
1 White/Green 3 Tx +
2 Green 3 Tx -
3 White/Orange 2 Rec +
4 Blue 1
5 White/Blue 1
6 Orange 2 Rec -
7 White/Brown 4
8 Brown 4

EIA/TIA 568B RJ45 plug pinout
Pin # Color Pair Signal
1 White/Orange 2 Tx +
2 Orange 2 Tx -
3 White/Green 3 Rec +
4 Blue 1
5 White/Blue 1
6 Green 3 Rec -
7 White/Brown 4
8 Brown 4

EIA/TIA 568B 10baseT cross-over cable
RJ45 Pair Color RJ45
1 2 White/Orange 3
2 2 Orange 6
3 3 White/Green 1
4
5
6 3 Green 2
7
8

RJ45 serial roll-over cable
RJ45 RJ45
1 8
2 7
3 6
4 5
5 4
6 3
7 2
8 1

DB25 to RJ45 DCE Cisco router console port adapter
RJ45 Color DB25
1 Blue 4
2 Orange 20
3 Black 3
4 Red 7
5 Green 1
6 Yellow 2
7 Brown 8
8 White 5

Connecting Ethernet Equipment Together
Device 1 Device 2 Cable Type Full-Duplex Possible? Notes
Hub Computer Straight-Through No A
Computer Computer Cross-Over Yes D
Hub Hub Cross-Over No B
Router Hub Straight-Through No
Router Switch Straight-Through Yes D
Hub Switch Cross-Over No C
Switch Computer Straight-Through Yes D
Router Computer Cross-Over Yes D

Notes:

A) "Computer" refers to PCs, Workstations, etc. ie. a device that has a NIC in it.

B) Many hubs have a MDI/MDI-X button that controls one of the ports (usually the 1st one), if the button on one of the hubs is set so that the port is in MDI mode, then a straight through cable can be used to connect the hubs rather than a cross-over cable.

C) The same as 'B', if the hub has it's port set to MDI mode then it can connect to a switch port with a straight-through cable.

D) For Full-Duplex to work, both devices must be capable of Full-Duplex mode.