Ethernet 10base-T / 100base-TX pinout. Widely used in ethernet network devices. Same connector and pinout for both 10Base-T, 100Base-TX and 1000base-T.

Nowdays ethernet is a most common networking standard for LAN (local area network) communication, officially standardized by IEEE standard 802.3. Nowdays ethernet runs at 10Mb (10base-T), 100Mb (100Base-T) or 1Gb (1000Base-T) per second. It was originally developed by Xerox Corporation in cooperation with DEC and Intel in 1976. Ethernet uses a bus (old coaxial cable) or star topology (standard UTP cable). Most ethernet networks use unshielded twisted pair (UTP) cable. Category 5 (CAT5) cable widely used, but other variations are available. EIA/TIA specifies RJ-45 connectors - properly called 8P8C - (ISO 8877) for UTP (unshielded twisted pair) cable. (RJ45 refers to a set of connectors beyond the 8P8C standard but the former has replaced the latter in common usage).

Pin Description 10base-T 100Base-T 1000Base-T
1 Transmit Data+ or BiDirectional TX+ TX+ BI_DA+
2 Transmit Data- or BiDirectional TX- TX- BI_DA-
3 Receive Data+ or BiDirectional RX+ RX+ BI_DB+
4 Not connected or BiDirectional n/c n/c BI_DC+
5 Not connected or BiDirectional n/c n/c BI_DC-
6 Receive Data- or BiDirectional RX- RX- BI_DB-
7 Not connected or BiDirectional n/c n/c BI_DD+
8 Not connected or BiDirectional n/c n/c BI_DD-

Length of CAT5 cable runs should not exceed 100 meters.

Please note that it is very important that a single pair be used for pins 1 and 2; 3 and 6, 4 and 5 (if used), 7 and 8 (if used) in any common straight-thru UTP Cat5 network cable. If not, performance will degrade. Also note that TX & RX should be swapped if two computers are connected without switch/hub  and for connecting some devices without MDI-X autosensing (see UTP crossover cable).

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8 pin RJ45 (8P8C) female connector layout
8 pin RJ45 (8P8C) female connector
at the network interface cards/hubs
8 pin RJ45 (8P8C) male connector layout
8 pin RJ45 (8P8C) male connector
at the cables