ethernet Chapter 4

objectives Upon completion of this chapter, you should be able to: Describe how data accesses the media on Ethernet Select the correct network device for an Ethernet network Connect the proper media for an Ethernet network Select the correct cable type for connecting devices Troubleshoot & resolve network connectivity

4.1 ethernet

topology What was the old, original Ethernet physical topology? Bus What is the current Ethernet physical topology? Star or Extended Star What is the logical topology for current Ethernet using a hub? Bus/broadcast (sent to all on segment) What is the logical topology for current Ethernet using a switch? Star (sent only to destination device) Ethernet can use copper twisted pair or fiber cabling.

Ethernet access method Data on Ethernet networks shares the cable How can all devices communicate on this shared media?

csma Ethernet is contention-based/non-deterministic Data contends or shares for a spot on the media Doesn’t know when it’ll get access to it Listens for signal on media No signal = transmit data Transmit at same time= collision Devices do not keep track of whose turn it is More collisions= less throughput SOLUTION: CSMA/CD Deterministic takes turns. Non-deterministic does not take turns.

Csma/cd on ethernet networks Listens for silence Silence= transmit data If devices transmit at same time, collision They send a jam signal Backoff random time, listen for silence, retransmit Collisions not a problem much anymore Using switches & full-duplex, this is not a problem anymore This is like using walkie-talkies. If no one is talking, you press the button to speak. Collisions are a naturally occurring event. Your goal is to keep collisions to a minimum. To do that you have to keep network segments small and use a switch.

Current switched network 1st picture: NO COLLISIONS 2nd picture: SOME COLLISIONS because of the hub

duplexing Hubs Switch Send data out all ports Are dumb & can’t handle in/out HALF DUPLEX ONLY Switch Intelligent FULL DUPLEX Sends & receives at the same time

Frame size Min. frame size is 64 bytes; max is 1518 bytes Data is 46-1500 bytes > 64 bytes is considered a collision fragment & will be dropped Note there are different types/speeds of Ethernet. The frame structure for each is nearly identical. Ethernet II is used in TCP/IP networks. Padding can be added to make sure the data part is at least 46 bytes. PREAMBLE- used timing/synchronization of the frame between send & receiver. Basically saying., “Here comes a frame!” FCS or CRC- must match on destination NIC to show it received a complete frame

activity TestOut 4.1 4.1.1 4.1.2- Fact Sheet 4.1.3- Quiz (4Q)

Review- 4Q What important addresses are encapsulated into a frame? Source & destination MAC What does the preamble used for? Timing/synchronization What is the minimum frame size? 64 bytes What happens if a frame is less than 64 bytes? Considered a fragment & dropped

Ethernet specifications 4.2 Ethernet specifications

Ethernet standards for copper Speed; Baseband; Twisted Pair 100Base-T Fast Ethernet (Cat 5 or higher) 1000Base-T (Cat 5e or higher) 1000Base-TX (Cat 6 or higher) 100m max; Cat 6 less than 100m; Cat6a 100m Cx= using STP cable

Ethernet standards for fiber L= LONG; S= SHORT; Ex= EXTENDED REACH L & Ex are Single Mode (long distance) S is Multimode (shorter distance) Over 2000m, you must use single mode cable. W= compatible with SONET

Other ethernet standards SONET Uses fiber to multiplex signals over a cable over MUCH longer distances for a WAN Ethernet over HDMI Data shared over an Ethernet Channel (HEC) without using extra cables Ethernet over Power Line Sends data over AC lines on different frequency Use instead of running cable PoE requires Cat5 or better and devices that support it.

activity Review 4.2.2 Fact Sheet Lab 4.2.3 Reconnect to an Ethernet Network 4.2.4 Quiz (15 questions)

Review- 3q If a fiber cable has an L or Ex, which type of fiber cable is it? Single mode 1000Base-Tx is what category of Ethernet? Cat 6 You need to use PoE to some switches. Which of these Ethernet standards will work; 100Base-Fx, 1000Base-T, 10GBase-LR, 1000Base-Lx? 1000Base-T (all the others are fiber)

Connecting network devices 4.3 Connecting network devices

Which cable? Choose the correct cable: Crossover cable used to connect two switches/hubs using a regular port. Rollover & terminal emulation software. Auto MDI or MDIX means it will autosense & use whichever cable you plug in.

Uplink port Uplink Port (Internet Port) Allows you to connect one device to another, like switch to switch or hub to hub for when you run out of ports Uplink port on switch 1 to regular port on other switch using a straight through cable Show the hub with uplink port switch. Uplink to uplink port needs a crossover cable. Proper hookup would be uplink to regular port using a straight through cable.

activity Lab 4.3.3 Connect Network Devices 4.3.4 Quiz (10 Questions)

Review- 3q What happens when the CSMA/CD network detects a collision? Signals a collision, waits to check for silence, retransmits The data part of an Ethernet frame is 36 bytes. What needs to be added to the frame and how many bytes will the data need to be? Padding; 46 bytes A port on a switch is labeled Auto-MDIX. What does that mean? It will autosense the cable

Troubleshooting physical connectivity 4.4 Troubleshooting physical connectivity

Troubleshooting the link status Usually 2 lights on NIC/port Link Green- getting full 1Gbps Orange- only getting 100Mbps Red- possibly using wrong cable None- no connection Activity Flashing- data being sent/received Speed Activity- even if nothing is being transmitted, a heartbeat signal is sent periodically.

activity Watch 4.4.1- Troubleshooting the Fault Domain Lab 4.4.5- Exploring Physical Connectivity Lab 4.4.6- Troubleshoot Physical Connectivity 1 Lab 4.4.7- Troubleshoot Physical Connectivity 2 Lab 4.4.8- Troubleshoot Physical Connectivity 3 Lab 4.4.9- Troubleshoot Physical Connectivity 4 4.4.10 Quiz (15 questions)

Review- 3q If you connect a cable from a switch’s uplink to port 1 on another switch, which cable should you use? Straight through What does it mean if the NIC’s activity light is flashing? Data is being sent/received If you need to connect a laptop to a router to configure it, what do you need? Rollover/console cable & terminal emulation software

ethernet Chapter 4