Ethernet media and connector requirements / Connection media

Ethernet media and connector requirements
5.1.3 This page provides important considerations for an Ethernet implementation. These include the media and connector requirements and the level of network performance.


The cables and connector specifications used to support Ethernet implementations are derived from the EIA/TIA standards. The categories of cabling defined for Ethernet are derived from the EIA/TIA-568 SP-2840 Commercial Building Telecommunications Wiring Standards.

Figure compares the cable and connector specifications for the most popular Ethernet implementations. It is important to note the difference in the media used for 10-Mbps Ethernet versus 100-Mbps Ethernet. Networks with a combination of 10- and 100-Mbps traffic use Category 5 UTP to support Fast Ethernet.

The next page will discuss the different connection types.

Connection media
5.1.4 This page describes the different connection types used by each physical layer implementation, as shown in Figure . The RJ-45 connector and jack are the most common. RJ-45 connectors are discussed in more detail in the next section.


The connector on a NIC may not match the media to which it needs to connect. As shown in Figure , an interface may exist for the 15-pin attachment unit interface (AUI) connector. The AUI connector allows different media to connect when used with the appropriate transceiver. A transceiver is an adapter that converts one type of connection to another. A transceiver will usually convert an AUI to an RJ-45, a coax, or a fiber optic connector. On 10BASE5 Ethernet, or Thicknet, a short cable is used to connect the AUI with a transceiver on the main cable.

The next page will discuss UTP cables.

UTP implementation
5.1.5 This page provides detailed information for a UTP implementation.


EIA/TIA specifies an RJ-45 connector for UTP cable. The letters RJ stand for registered jack and the number 45 refers to a specific wiring sequence. The RJ-45 transparent end connector shows eight colored wires. Four of the wires, T1 through T4, carry the voltage and are called tip. The other four wires, R1 through R4, are grounded and are called ring. Tip and ring are terms that originated in the early days of the telephone. Today, these terms refer to the positive and the negative wire in a pair. The wires in the first pair in a cable or a connector are designated as T1 and R1. The second pair is T2 and R2, the third is T3 and R3, and the fourth is T4 and R4.

The RJ-45 connector is the male component, which is crimped on the end of the cable. When a male connector is viewed from the front, the pin locations are numbered from 8 on the left to 1 on the right as seen in Figure .

The jack is the female component in a network device, wall outlet, or patch panel as seen in Figure . Figure shows the punch-down connections at the back of the jack where the Ethernet UTP cable connects.

For electricity to run between the connector and the jack, the order of the wires must follow T568A or T568B color code found in the EIA/TIA-568-B.1 standard, as shown in Figure . To determine the EIA/TIA category of cable that should be used to connect a device, refer to the documentation for that device or look for a label on the device near the jack. If there are no labels or documentation available, use Category 5E or greater as higher categories can be used in place of lower ones. Then determine whether to use a straight-through cable or a crossover cable.

If the two RJ-45 connectors of a cable are held side by side in the same orientation, the colored wires will be seen in each. If the order of the colored wires is the same at each end, then the cable is a straight-through, as seen in Figure .

In a crossover cable, the RJ-45 connectors on both ends show that some of the wires are connected to different pins on each side of the cable. Figure shows that pins 1 and 2 on one connector connect to pins 3 and 6 on the other.

Figure shows the guidelines that are used to determine the type of cable that is required to connect Cisco devices.

Use straight-through cables for the following connections:

• Switch to router
• Switch to PC or server
• Hub to PC or server

Use crossover cables for the following connections:

• Switch to switch
• Switch to hub
• Hub to hub
• Router to router
• PC to PC
• Router to PC

The category of UTP cable required is based on the type of Ethernet that is chosen.

The next page explains how repeaters work.