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Networking Fundamentals · Foundational

Registered Jack 45 (RJ45)

The common name for the eight-position, eight-contact (8P8C) modular connector used on Ethernet twisted-pair cables.

Definition

Strictly, RJ45 was a telephone wiring specification and the Ethernet connector is 8P8C, but the industry uses RJ45 for both. Cables are terminated to T568A or T568B pinouts. Pins 1, 2, 3 and 6 carry 10/100 data, while Gigabit and faster use all eight pins.

Example

A crimper attaches an RJ45 plug to the end of a Cat 6 cable.

Exam tip

RJ45 has 8 pins and is wider than the 6-position RJ11 telephone connector.

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