Cabling the LANs 209 Table 4-3 Comparing Ethernet Media Requirements Media Maximum Segment Length Topology Connector 10BASE2 50-ohm coaxial (thinnet) 185 m (606.94 feet) Bus British Naval Connector (BNC) 10BASE5 50-ohm coaxial (thicknet) 500 m (1640.4 feet) Bus Attachment unit interface (AUI) 10BASE-T EIA/TIA CAT 3, 4, 5 UTP, two pair 100 m (328 feet) Star ISO 8877 (RJ-45) 100BASE-TX EIA/TIA CAT 5 UTP, two pair 100 m (328 feet) Star ISO 8877 (RJ-45) 100BASE-FX 62.5/125 multimode fiber 400 m (1312.3 feet) Star Duplex media interface connector (MIC) straight tip (ST) connector or subscriber connector (SC) 1000BASE-CX STP 25 m (82 feet) Star ISO 8877 (RJ-45) 1000BASE-T EIA/TIA CAT 5 UTP, four pair 100 m (328 feet) Star ISO 8877 (RJ-45) 1000BASE-SX 62.5/50 micro multimode fiber 275 m (853 feet) for 62.5 micro fiber; 550 m (1804.5 feet) for 50 micro fiber Star SC 1000BASE-LX 62.5/50 micro multimode fiber; 9-micron single- mode fiber 440 m (1443.6 feet) for 62.5 micro fiber; 550 m (1804.5 feet) for 50 micro fiber; 3 to 10 km (1.86 to 6.2 miles) on single-mode fiber Star SC chpt_04.fm Page 209 Tuesday, May 27, 2003 9:01 AM 210 Chapter 4: Cable Testing and Cabling LANs and WANs Figure 4-20 Differentiating Among Connections Connection Media This section briefly discusses the connection types used by physical layer implementa- tion and an interface device, Gigabit Interface Converter (GBIC), used between the Ethernet and fiber-optic systems. This section covers the following topics: ■ RJ-45—A connector commonly used for finishing a twisted-pair cable ■ AUI—A connector that interfaces between a computer’s NIC or router interface and an Ethernet cable ■ GBIC—A device used as an interface between the Ethernet and fiber-optic systems RJ-45 The RJ-45 connector and jack are the most prevalent. RJ-45 connectors are discussed in more detail in the section, “UTP Implementation” later in the chapter. Attachment Unit Interface In some cases, the type of connector on a NIC does not match the type of media that it needs to connect to. An interface exists for the AUI connector. The AUI is the 15-pin physical connector interface between a computer’s NIC and Ethernet cable. On 10BASE5 (thicknet) Ethernet, a short cable is used to connect the AUI on the computer with a transceiver on the main cable. In 10BASE2 (thinnet) Ethernet networks, the NIC con- nects directly to the Ethernet coaxial cable at the back of the computer. Gigabit Interface Converter A Gigabit Interface Converter (GBIC) is a hot-swappable input/output device that plugs into a Gigabit Ethernet port. A key benefit of using a GBIC is that GBICs are interchangeable. This feature gives users the flexibility to deploy other 1000BASE-X technology without needing to change the physical interface/module on the router or switch. chpt_04.fm Page 210 Tuesday, May 27, 2003 9:01 AM Cabling the LANs 211 The fiber-optic GBIC is a transceiver that converts serial electric currents to optical sig- nals and that also coverts optical signals to digital electric currents. Some of the optical GBICs include the following: ■ Short wavelength (1000BASE-SX) ■ Long wavelength/long haul (1000BASE-LX/LH) ■ Extended distance (1000BASE-ZX) Typically, the GBIC is used as an interface between the Ethernet and fiber-optic systems, such as Fiber Channel and Gigabit Ethernet. Figure 4-21 shows a GBIC, and Figure 4-22 shows a Cisco WS-X2931 Gigabit Ethernet Module with the GBIC out. Figure 4-21 Gigabit Interface Converter (GBIC) Figure 4-22 Cisco WS-X2931 Gigabit Ethernet Module with GBIC Out chpt_04.fm Page 211 Tuesday, May 27, 2003 9:01 AM 212 Chapter 4: Cable Testing and Cabling LANs and WANs UTP Implementation If you look at the RJ-45 transparent end connector, you can see eight colored wires. These wires are twisted into four pairs. Four of the wires (two pairs) carry the positive, or true, voltage and are considered “tip” (T1 through T4); the other four wires carry the inverse, or false, voltage grounded and are called “ring” (R1 through R4). 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, and so on. The RJ-45 plug is the male component, crimped at the end of the cable. As you look at the male connector from the front, with the clip facing down, the pin locations are numbered from 8 on the left down to 1 on the right, as shown in Figure 4-23. The jack, shown in Figure 4-24, is the female component in a network device, wall or cubi- cle partition outlet, or patch panel. As you look at the device port, the corresponding female pin locations are 1 on the left up to 8 on the right. Figure 4-23 Pin Locations on the RJ-45 Connector For electricity to run between the connector and the jack, the order of the wires must fol- low EIA/TIA-568-A and EIA/TIA-568-B standards, as shown previously in Figure 4-16. In addition to identifying the correct EIA/TIA category of cable to use for a connecting device (which depends on what standard is being used by the jack on the network device), you need to determine which of the following to use: ■ A straight-through cable—A cable that maintains the pin connection all the way through the cable. Thus, the wire connected to pin 1 is the same on both ends of the cable. ■ A crossover cable—A cable that crosses the critical pair to properly align, trans- mit, and receive signals on the device with line connections. chpt_04.fm Page 212 Tuesday, May 27, 2003 9:01 AM Cabling the LANs 213 Figure 4-24 RJ-45 Jack and Wire Order If the two RJ-45 ends of a cable are held side by side in the same orientation, the col- ored wires (or strips or pins) are seen at each connector end. If the order of the colored wires is the same at each end, the cable is straight-through. Figure 4-25 illustrates that the RJ-45 connectors on both ends show all the wires in the same order. Figure 4-25 UTP Implementation: Straight-Through Cable chpt_04.fm Page 213 Tuesday, May 27, 2003 9:01 AM 214 Chapter 4: Cable Testing and Cabling LANs and WANs Specified for Ethernet, in a CAT 5 UTP cable, only wires 1, 2, 3, and 6 are used for transmit (TD) and receive (RD) signals. The other four wires are not used. As shown on the left of Figure 4-25, in a straight-through cable, the RJ-45 pins 1, 2, 3, and 6 at one end are connected to pins 1, 2, 3, and 6 at the other end of the connection. Gigabit Ethernet, however, uses all eight wires. You can use a straight-through cable to connect devices such as PCs or routers to other devices used as hubs or switches. As Figure 4-26 shows, you should use straight-through when only one port is designated with an x. Figure 4-26 Interconnecting Devices Using Straight-Through Cable With crossover cable, the RJ-45 connectors on both ends show that some of the wires on one side of the cable are crossed to a different pin on the other side of the cable. Specifically for Ethernet, pin 1 at one RJ-45 end should connect to pin 3 at the other end. Pin 2 at one end should connect to pin 6 at the other end, as shown in Figure 4-27. Figure 4-27 UTP Implementation—Crossover chpt_04.fm Page 214 Tuesday, May 27, 2003 9:01 AM Cabling the LANs 215 You can use a crossover cable to connect similar devices, switch to switch or switch to hub. Figure 4-28 shows that you use a crossover cable when both ports are designated with an x or when neither port is designated with an x. Figure 4-28 Interconnecting Devices Using Crossover Cable The following are the guidelines for the type of cable to use when interconnecting net- working devices. Use straight-through cables for the following cabling: ■ Switch to router ■ Switch to PC or server ■ Hub to PC or server Use crossover cables for the following cabling: ■ Switch to switch ■ Switch to hub ■ Hub to hub ■ Router to router ■ PC to PC ■ Router to PC Lab Activity Punch-Down Jacks In this lab, you learn to wire an RJ-45 data jack for installation in a wall plate using a punch-down tool. chpt_04.fm Page 215 Tuesday, May 27, 2003 9:01 AM 216 Chapter 4: Cable Testing and Cabling LANs and WANs LAN Connection Devices Many types of devices are connected to make up a LAN. These are called the LAN hardware components. This section discusses some of the common hardware compo- nents that are used in a LAN environment. LAN devices can include repeaters, hubs, bridges, switches, and routers with switches being the most prevalent device in modern LANs. Repeaters As mentioned in the section, “LAN Physical Layer” and shown in Figure 4-19, many types of media exist, and each one has advantages and disadvantages. One of the dis- advantages of the CAT 5 UTP cable that is primarily used is cable length. The maximum length for UTP cable in a network is 100 meters (approximately 333 feet). If you have to expand the network beyond that limit, you need to add a repeater. In most Ethernet networks this repeater normally takes the form of hub, which is a multiport repeater, or a newer technology switch. The term repeater comes from the early days of visual communication when a person situated on a hill would repeat the signal that was just received from the person on the previous hill to communicate the signal to the person on the next hill. Telegraph, tele- phone, microwave, and optical communications all use repeaters to strengthen their signals over long distances. The purpose of a repeater, shown in Figures 4-29 and 4-30, is to regenerate and retime network signals at the bit level to allow them to travel a longer distance on the media. Repeaters are commonly used if too many network nodes exist or the number of cables is insufficient. The Four Repeater Rule for 10 Mbps bus-based Ethernet, also know as the 5-4-3 Rule, is used as a standard when extending LAN segments. This rule states that no more than five network segments can be connected end-to-end using four repeaters, but only three segments can have hosts (computers) on them. Although the 5-4-3 rule is important when applied to bus-based networks, it does not have much validity with switches and extended star topologies. chpt_04.fm Page 216 Tuesday, May 27, 2003 9:01 AM LAN Connection Devices 217 Figure 4-29 Repeaters Figure 4-30 Repeaters Connect Two End Nodes Hubs Hubs are actually multiport repeaters. In many cases, the difference between the two devices is the number of ports that each provides. While a typical repeater has just 2 ports, a hub generally has from 4 to 24 ports, as shown in Figure 4-31. Additionally, hubs are most commonly used in Ethernet 10BASE-T or 100BASE-T networks, although other network architectures use them as well. chpt_04.fm Page 217 Tuesday, May 27, 2003 9:01 AM 218 Chapter 4: Cable Testing and Cabling LANs and WANs Figure 4-31 Eight-Port Hub Using a hub changes the network topology from a linear bus, where each device plugs directly into the wire, to a star. With hubs, data arriving over the cables to a hub port is electrically repeated on all the other ports connected to the same network segment, except for the port on which the data was sent. Hubs come in two basic types: ■ Active—An active hub must be plugged into an electrical outlet because it needs power to amplify the incoming signal before passing it out to the other ports. ■ Intelligent—An intelligent hub are sometimes called smart hubs. These devices basically function as active hubs, but also include a microprocessor chip and diagnostic capabilities. They are more expensive than active hubs, but are useful in troubleshooting situations. All devices that are attached to a hub hear all traffic. Therefore, hubs maintain a single collision domain. A collision is a situation where two end stations send data over the network wire at the same time. Sometimes, hubs are called concentrators because they serve as a central connection point for an Ethernet LAN. Bridges At times, you need to break up a large LAN into smaller, more easily managed seg- ments. This strategy decreases the amount of traffic on a single LAN and can extend Lab Activity Hubs Purchase In this lab, you are introduced to the variety and prices of network compo- nents out in the market. This lab looks specifically at Ethernet hubs and NICs. chpt_04.fm Page 218 Tuesday, May 27, 2003 9:01 AM . (RJ-45) 10 0BASE-FX 62. 5 / 12 5 multimode fiber 400 m (13 12. 3 feet) Star Duplex media interface connector (MIC) straight tip (ST) connector or subscriber connector (SC) 10 00BASE-CX STP 25 m ( 82 feet). Cisco WS-X29 31 Gigabit Ethernet Module with the GBIC out. Figure 4- 21 Gigabit Interface Converter (GBIC) Figure 4 -22 Cisco WS-X29 31 Gigabit Ethernet Module with GBIC Out chpt_04.fm Page 21 1 Tuesday,. signals on the device with line connections. chpt_04.fm Page 21 2 Tuesday, May 27 , 20 03 9: 01 AM Cabling the LANs 21 3 Figure 4 -24 RJ-45 Jack and Wire Order If the two RJ-45 ends of a cable are held