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Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Ethernet Basics Chapter 4 Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Objectives • Define and describe Ethernet • Explain early Ethernet implementations • Describe ways to extend and enhance Ethernet networks Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Introduction • Networks did not exist when computers were first created – Sneakernet was the method of moving files – A more efficient method of sharing data was developed Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Historical/Conceptual Ethernet Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) The First Ethernet Implementation • • • • • Developed by Xerox in 1973 Based on bus topology Transferred data at 3Mbps max Remained in-house technology until 1979 Evolved into today’s Ethernet standards Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) The Next Iteration of the Ethernet • DIX (Digital-Intel-Xerox) standard – Transferred data at 10Mbps max • DEC, Intel, and Xerox transferred control of the Ethernet standard to IEEE – 802.3 (Ethernet) committee Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Issues Faced by Ethernet’s Designers • How to send data across the wire • How to identify the sending and receiving computers • How to determine which computer should use shared cable at what time Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Topology • Hybrid star-bus • Hub at the center – Electronic repeater – Repeats the same signal out to the other connected ports – Does not send signal back down the originating port – Repeaters are not amplifiers Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.1 Ethernet hub Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Test Specific Organizing the Data: Ethernet Frames Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Ethernet Frames • Smaller pieces of data transmitted between computers • Using frames addresses two networking issues – Prevents any single machine from monopolizing the shared bus cable – Makes retransmitting lost data more efficient • Used by all networking technologies (including Ethernet) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.2 Ethernet frame Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Preamble and MAC addresses • Preamble – Beginning of each frame – Seven bytes of alternating ones and zeros • Start frame – Follows the preamble – One byte • MAC address – Unique identifying address for each node Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.3 Frames propagating on a network Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) NICs • Ethernet security vulnerability – Sniffers can order a NIC to run in promiscuous mode • NIC processes all frames, not only those intended for its MAC address – Sniffers have legitimate uses, but may also be used unscrupulously Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Type and Data • Type – Helps receiving computer interpret the frame contents at a basic level ►IPv4 or IPv6 data • Data – Part of the frame that contains the payload – If an IP packet, packet contains extra information such as the IP addresses of both systems Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Pad and the Frame Check Sequence • Pad – Minimum Ethernet frame size is 64 bytes – Extra data added if frame has fewer than 64 bytes • Frame check sequence – Aids in determining if the data has been damaged in transit – Calculation used at the beginning and at the end of transmission must give same result Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Network Access • Carrier sense – Each node checks to see whether cable is in use – Sends the frame when cable is free • Multiple access – All machines have equal access to the wire – Collision occurs if two machines send frame simultaneously Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) CSMA/CD Carrier Sense Each NIC on the network examines the wire before sending a frame. If the node detects traffic, it will pause a random amount of time and try again. Copyright © 2015 by McGraw-Hill Education. All rights reserved. Multiple Access All machines have equal access to the wire. Access to the wire is on a firstcome, first-served basis Collision Detection If two NICs transmit at the same time, a collision results. NICs may listen to detect a collision. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.4 No one else is talking—send the frame! Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.5 Collision! Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Collisions • When collision occurs – Both machines generate a random number to determine delay time before resending packet • Properly running Ethernet network has a maximum collision rate of 10 percent • Collision domain – A group of nodes that could send frames at the same time ►could potentially cause a collision Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.6 Rolling for timing Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Early Ethernet Networks Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Bus Ethernet • Original Ethernet networks used a true bus topology • Thicknet (10Base5) • Thinnet (10Base2) – The T connector enabled the bus to carry a single electrical signal that connected every device on the network • The ends of the bus have to be terminated Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.7 Thicknet vampire tap Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.8 10Base2 T connector in action Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.9 Terminating resistor Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) 10BaseT: Physical vs. Logical • Over 99 percent of all networks use 10BaseT or its newer versions • Consists of two or more computers connected to a central hub • NICs connect with wires per 802.3 standards • Hubs for 10BaseT – Vary in size, shape, and number of ports – All need electrical power Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) 10BaseT Speed 10 Mbps Copyright © 2015 by McGraw-Hill Education. All rights reserved. Signal Type Baseband A single signal on the cable Type of cable Twisted Pair Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.10 Two 10BaseT hubs Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) 10BaseT: UTP • Uses CAT 3 or higher • Two pairs of wires required (four-pair cable commonly used) • One pair of wires sends data to the hub • The other pair receives data from the hub Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.11 A typical four-pair CAT 5e unshielded twisted-pair cable Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Check Your CATS! • RJ-45 Connector – Used in 10BaseT – Each pin connects to a single wire inside the cable – Pins are numbered from one to eight Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.12 Two views of an RJ-45 connector Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.13 The pins on an RJ-45 connector are numbered 1 through 8 Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Check Your CATS! (cont’d.) • RJ-45 pin assignments – 1 and 2 send data – 3 and 6 receive data – Duplex versus half-duplex mode • RJ-45 connector is called a crimp – Crimping is the act of installing an RJ-45 connector – A crimper is the tool used • Wires are color-coded Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.14 Color-coded pairs Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) TIA/EIA 568A and 568B • TIA/EIA defines industry standards for correct crimping • Advantage of following an established color code scheme – Ensures wires match up correctly at each end of the cable • Network technicians can make their own Ethernet cables Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.15 The TIA/EIA 568A and 568B standards Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) 10BaseT Limits and Specifications • Maximum distance between hub and computer: 100 meters • No more than 1024 computers connected to one hub – Such a high number is too expensive and not practical – Excessive collisions can easily bog down Ethernet performance Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) 10BaseT Summary • • • • • Speed: Signal type: Distance: Node limit: Topology: • Cable type: Copyright © 2015 by McGraw-Hill Education. All rights reserved. 10 Mbps Baseband 100 meters between hub/node 1024 nodes per hub Star-bus topology: physical star, logical bus CAT3 or better UTP cabling with RJ-45 connectors Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) 10BaseFL • Fiber-optic version • Increased maximum distance – Two kilometers between the hub and the node • Immune to electrical interference • More secure because difficult to tap into • Multimode fiber-optic cables with ST or SC connectors Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.16 Typical 10BaseFL card Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) 10BaseFL Summary • • • • • Speed: Signal type: Distance: Node limit: Topology: • Cable type: Copyright © 2015 by McGraw-Hill Education. All rights reserved. 10Mbps Baseband 2000 meters between hub/node 1024 nodes per hub Star-bus topology: physical star, logical bus Multimode fiber-optic cabling with ST or SC connectors Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Media Converters • 10BaseT and 10BaseFL have different cabling and hubs but same Ethernet packets • A media converter connects different Ethernet types Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.17 Typical copper-to-fiber Ethernet media converter (photo courtesy of TRENDnet) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Extending and Enhancing Ethernet Networks Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) General Tips • Install additional hubs to connect multiple LANs • Use a network bridge to connect two Ethernet networks • Replace hubs with better devices to reduce collisions Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Coupler • Device with female connectors on both ends • Used to connect a machine in a location not planned for in original network • Examples of coupler types – BNC couplers – UTP couplers Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Connecting Ethernet Segments • When all ports on an existing hub have been used, add another hub or a bridge – Hubs can be connected using an uplink port or a crossover cable • Uplink ports – Connect two hubs using a straight-through cable Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.19 Typical uplink port Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Connecting Hubs • When connecting hubs: – You can only daisy-chain hubs – Take time to figure out the uplink ports – If you plug hubs in incorrectly, no damage will occur (they just won’t work) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.20 Daisy-chained hubs Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.21 A hierarchical hub configuration will not work! Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.22 Press-button port Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Crossover Cables • Another way to connect two hubs • Connect via two normal ports using one crossover cable • Reverse sending and receiving pairs on one end – One end crimped per TIA/EIA 568A – Second end crimped per TIA/EIA 568B Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.23 A crossover cable reverses the sending and receiving pairs Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Bridge • Acts like a repeater or hub to connect two Ethernet segments • Goes one step beyond a repeater or hub – Filters and forwards traffic • At first, acts like a repeater or hub • Monitors and records network traffic – Then begins to filter and forward Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Switched Ethernet Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) The Trouble with Hubs • Classic 10BaseT network can only have one message on the wire at a time • Collisions slow the effective transmission speed for the whole network • Ethernet switch – Creates point-to-point connections between two conversing computers Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.24 Hub (top) and switch (bottom) comparison Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Switches to the Rescue • Ethernet switches give every conversation the full bandwidth of the network • Source Address Table (SAT) – A switch copies the source MAC addresses and builds a table of MAC addresses of each connected computer Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.25 A switch tracking MAC addresses Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.26 A switch making two separate connections Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.27 Switches are very commonly connected in a tree organization Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Spanning Tree Protocol (STP) • Eliminates the problem of accidental bridge loops (i.e., redundant connections in a network) • With STP enabled: – Loops are detected – Looped port’s state is set to blocking Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Figure 4.28 A bridging loop Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Spanning Tree Protocol (cont’d.) • STP-enabled switches use a Bridge Protocol Data Unit (BPDU) frame – Determines distance between them – Helps keep track of changes on the network • Rapid Spanning Tree Protocol (RSTP), 802.1w replaced the original STP in 2001 Copyright © 2015 by McGraw-Hill Education. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N10-006) Troubleshooting Hubs and Switches • Problem categories – Physical damage, dead ports, or general flakiness • Hub or switch might have problems if device can’t connect to the network • Check for link lights • Check cables • Replace hub or switch with a known-good device Copyright © 2015 by McGraw-Hill Education. All rights reserved.