Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Network Troubleshooting Chapter 21

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Describe appropriate troubleshooting tools and their functions Analyze and discuss the troubleshooting process Resolve common network issues Describe the Internet of Things Objectives

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Test Specific Troubleshooting Tools

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Required tools vary depending on the job type Always consider the safety of your data first – Before beginning troubleshooting Many software diagnostic tools are available – You may not need any purchased software tools Troubleshooting Tools

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Cable testers, TDRs, and OTDRs Certifiers Voltage event recorders Protocol analyzers Cable strippers Multimeters Tone probes/generators Hardware Tools

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Line testers Butt sets Punchdown tools Hardware Tools (cont’d.)

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Open circuit – Cable wires do not connect from one end of the cable to the other Short circuit – Connection between wires in a cable Wire map problem – Wires do not connect to the proper location on the jack or plug Potential Circuit Problems

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Crosstalk – The electrical signal from one wire pair causes interference in a nearby wire pair Noise – Spurious signals typically due to faulty hardware or poorly crimped jacks Impedance mismatch – Can occur where cables of different types connect Potential Circuit Problems (cont’d.)

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Cable testers – Help identify continuity or wire map problems TDRs (time domain reflectometers) – Locate copper cable breaks OTDRs (optical time domain reflectometers) – Locate fiber-optic cable breaks Cable Testers, TDRs, and ODTRs

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Figure 21.1 Typical cable tester

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Figure 21.2 An EXFO AXS-100 OTDR (photo courtesy of EXFO)

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Ensure a cable can handle its rated capacity – Use when a cable is not moving data as it should Require a loopback on the far end Problems that reduce cable capacity – Crosstalk – Attenuation – Interference Certifiers

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Measures light loss in a fiber optic cable – Uses a high-powered light source and detector Also called optical power meter Inherent impurities in the glass can reduce light transmission – Other causes: dust, poor connections, and light leakage Light Meter

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Figure 21.3 Fiberlink® 6650 Optical Power Meter (photo courtesy of Communications Specialties, Inc.)

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Detect power and heat problems Symptom: intermittent problems Possible cause: heat problems in server rooms A voltage event recorder can help identify problems with electricity A temperature monitor collects temperature information over time Voltage Event Recorder/ Temperature Monitor

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Monitor protocols running at different layers – Application, Session, Transport, Network, and Data Link May be hardware or software tools Protocol Analyzers

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Problem symptoms – A session fails to start – A DNS server fails to respond – Confusing information appears on the network – You suspect a rogue DHCP server exists – Excess or unexpected traffic slows the network Protocol Analyzers (cont’d.)

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Needed for making UTP cables – Also need crimpers Cable stripper and crimper can be combined in a single tool Cable Strippers/Snips

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Figure 21.4 A cable stripping and crimping tool

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Test AC and DC voltage, resistance, and continuity Often used for continuity testing when a cable tester is not available Multimeters

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Work together to help locate a particular cable A tone generator puts a signal (tone) on a wire A tone probe on opposite end detects the signal Tone Probes and Tone Generators

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. A telephone person’s best friend Tap into a 66- or 110-block to test a line Butt Sets

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Simple devices for checking telephone wiring integrity Possible outcomes when checking a twisted pair line – Good – Dead – Reverse wired – An AC voltage on the line Line Testers

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Put UTP wires into 66- and 110-blocks Repunch a connection to make sure contacts are set Punchdown Tools

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Figure 21.5 A punchdown tool in action

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Built-in tools – tracert/traceroute – ipconfig/ifconfig/ip – arp, ping, arping, and pathping – nslookup/dig – hostname – route – nbtstat and netstat/ss Software Tools

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Third-party tools – Packet sniffer – Port scanners – Throughput testers – Looking glass sites Software Tools (cont’d.)

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Traces all of the routers between two points Assist in diagnosing where a problem lies – For problems in reaching a remote system If traceroute stops at a certain router – Problem is the next router or the connection Some routers block ICMP packets containing traceroute information The tracert/traceroute Commands

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Tracing route to adsl dsl.hstntx.swbell.net [ ] over a maximum of 30 hops: 1 1 ms <1 ms 1 ms Router.totalhome [ ] 2 38 ms 41 ms 70 ms adsl dsl.hstntx.swbell.net [ ] Sample traceroute output

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Displays IP settings ipconfig without parameters – Provides basic information only ipconfig /all – Gives detailed information (e.g., DNS servers and MAC addresses) The ipconfig/ifconfig/ip Commands

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Ethernet adapter Main: Connection-specific DNS Suffix. : IPv6 Address : 2001:470:bf88:1:fc2d:aeb2:99d2:e2b4 Temporary IPv6 Address..... : 2001:470:bf88:1:5e4:c1ef:7b30:ddd6 Link-local IPv6 Address..... : fe80::fc2d:aeb2:99d2:e2b4%8 IPv4 Address : Subnet Mask : Default Gateway : fe80::223:4ff:fe8c:b720% Tunnel adapter Local Area Connection* 6: Media State : Media disconnected Connection-specific DNS Suffix. : Sample ipconfig output

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. lo0: flags=8049 mtu options=3 inet6 ::1 prefixlen 128 inet netmask 0xff inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1 nd6 options=1 gif0: flags=8010 mtu 1280 stf0: flags=0<> mtu 1280 en0: flags=8863 mtu 1500 options=10b ether 3c:07:54:7a:d4:d8 inet6 fe80::3e07:54ff:fe7a:d4d8%en0 prefixlen 64 scopeid 0x4 inet netmask 0xffffff00 broadcast inet6 2601:e::abcd:3e07:54ff:fe7a:d4d8 prefixlen 64 autoconf inet6 2601:e::abcd:b84e:9fad:3add:c73b prefixlen 64 autoconf temporary nd6 options=1 media: autoselect (1000baseT ) status: active Sample ifconfig output

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. 1: lo: mtu qdisc noqueue state UNKNOWN group default link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet /8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: mtu 1500 qdisc pfifo_fast state UNKNOWN group default qlen 1000 link/ether 00:0c:29:e0:b2:85 brd ff:ff:ff:ff:ff:ff inet /24 brd scope global eth0 valid_lft forever preferred_lft forever inet6 2601:e:0:abcd:8cfb:6220:ec23:80a/64 scope global temporary dynamic valid_lft 86221sec preferred_lft 14221sec inet6 2601:e:0:abcd:20c:29ff:fee0:b285/64 scope global dynamic valid_lft 86221sec preferred_lft 14221sec inet6 fe80::20c:29ff:fee0:b285/64 scope link valid_lft forever preferred_lft forever Sample Linux’s ip output

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. The ARP table records IP address–MAC address pairs The arp command enables viewing and changing the ARP table on a computer The arp Command

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Sample arp -a output Interface: ––– 0xc Internet Address Physical Address Type b8-9b-c9-7d-e7-76 dynamic b6-7e-ae-23 dynamic ab-cc-aa-fe-ed dynamic b d7-33 dynamic b-4b-4c-4d-4e-46 dynamic dynamic

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Queries by name or IP address Uses ICMP packets Works across routers Problem: devices can block ICMP Defaults to IPv4 – Use -6 switch for IPv6: ping -6 (Windows) or ping6 (Unix/Linux/OS X) The ping Command

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Pinging with 32 bytes of data: Reply from : bytes=32 time<1ms TTL=64 Ping statistics for : Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 0ms, Average = 0ms Sample ping output

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Uses ARP frames rather than ICMP packets Does not work across routers Is supported by UNIX and UNIX-like systems The arping Command

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. ARPING from eth0 Unicast reply from [00:1D:60:DD:92:C6] 0.875ms Unicast reply from [00:1D:60:DD:92:C6] 0.897ms Unicast reply from [00:1D:60:DD:92:C6] 0.924ms Unicast reply from [00:1D:60:DD:92:C6] 0.977ms Sample arping output

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Combines the functions of ping and tracert – Also adds some additional functions The pathping Command

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Sample pathping output Tracing route to xeroxpaser.totalhome [ ] Over a maximum 30 hops: 0 local-PC.totalhome [ ] 1 xrxphsr.totalhome [ ] Computing statistics for 25 seconds... Source to Here This Node/Link Hop RTT Lost/Sent – Pct Lost/Sent – Pct Address 0 local-PC.totalhome [ ] 0/ 100 – 0% : 10ms 0/ 100 – 0% 0/ 100 – 0% xrxphsr.totalhome [ ] Trace complete

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Both diagnose DNS problems nslookup (all operating systems) – Only choice by default on Windows systems dig (UNIX/Linux) – Provides more verbose output by default than nslookup – Example of the dig command: dig mx totalsem.com The nslookup/dig Commands

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. ; > DIG P2 > mx totalsem.com ;; global options: printcmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 6070 ;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1 ;; QUESTION SECTION: ;totalsem.com. IN MX ;; ANSWER SECTION: totalsem.com IN MX 10 mx1c1.megamailservers.com. totalsem.com IN MX 100 mx2c1.megamailservers.com. totalsem.com IN MX 110 mx3c1.megamailservers.com. Output for the dig command

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Simplest of all utilities covered here Returns name of host from which it runs hostname sample output: C:\> C:\>hostname mike-win8beta The hostname Command

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Dynamic (keeps running) Equivalent to traceroute Not supported by Windows The mtr Command

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. My traceroute [v0.73] totaltest ( ) Keys: Help Display mode Restart statistics Order of fields quit Packets Pings Host Loss% Snt Last Avg BestWrst StDev 1. Router.totalhome 0.0% adsl dsl.hstntx.s 0.0% Sample mtr output

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Used to display and edit the local system’s routing table Type route print or netstat -r The route Command

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. =========================================================================== Interface List d 60 dd 92 c Marvell 88E8056 PCI-E Ethernet Controller Software Loopback Interface 1 =========================================================================== IPv4 Route Table =========================================================================== Active Routes: Network DestinationNetmask Gateway Interface Metric On-link On-link On-link On-link On-link On-link On-link On-link On-link On-link On-link On-link On-link On-link On-link =========================================================================== Persistent Routes: None Sample route print output

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Windows-only program Command-line equivalent of Window’s My Network Places or Network icon Always run with a switch nbtstat –n shows the local NetBIOS names The nbtstat Command

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Main: Node IpAddress: [ ] Scope Id: [] NetBIOS Local Name Table Name Type Status MIKESPC UNIQUE Registered TOTALHOME GROUP Registered MIKESPC UNIQUE Registered TOTALHOME GROUP Registered Sample nbtstat -n output

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Comes with Windows systems Displays the current state of running IP processes Shows what sessions are active Provides statistics based on ports or protocols Type netstat to show only current sessions Type netstat –r to show the routing table; identical to route print The netstat Command

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Active Connections Proto Local Address Foreign Address State TCP :27015 MikesPC:51090 ESTABLISHED TCP :51090 MikesPC:27015 ESTABLISHED TCP :52500 MikesPC:52501 ESTABLISHED TCP : :27039 CLOSE_WAIT TCP : :http CLOSE_WAIT TCP :56126 acd :https ESTABLISHED TCP :62727 TOTALTEST:ssh ESTABLISHED TCP : :https TIME_WAIT TCP : :http ESTABLISHED Sample netstat output

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Has eclipsed netstat on the Linux side Faster and more powerful than netstat Sample output (filtered to show only TCP connections): State Recv-Q Send-Q Local Address:Port Peer Address:Port CLOSE-WAIT : :https CLOSE-WAIT : :https ESTAB : :http The ss Command

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Also called protocol analyzer or packet analyzer Intercepts and logs network packets Many choices – Software or dedicated hardware devices Software example: Wireshark Command-line tool: tcpdump Packet Sniffer

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Figure 21.6 Wireshark in action!

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Probe ports on another system Log the state of scanned ports Uses – Find unintentionally open ports that could make a system vulnerable to attack – Hackers can use to break into systems Nmap is available for UNIX and Windows Angry IP Scanner is a Windows port scanner Port Scanners

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Figure 21.7 Angry IP Scanner

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Measure the data flow in a network The appropriate tool depends on the type of network throughput you want to test Several speed-test sites are available for checking an Internet connection’s throughput – Example: MegaPath’s Speakeasy Speed Test Throughput Testers

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Figure 21.8 Speed Test results from Speakeasy

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Browser-accessible remote servers Contain collections of diagnostic tools – Also Border Gateway Protocol (BGP) query tools Allow selection of origination location, target destination, and desired diagnostic – May also test IP version Looking Glass Sites

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Do no harm. Always make good backups! Troubleshooting: Two Basic Rules

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. 1.Identify the problem a.Gather information b.Duplicate the problem, if possible c.Question users d.Identify symptoms e.Determine if anything has changed f.Approach multiple problems individually The Troubleshooting Process

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. 2.Establish a theory of probable cause a.Question the obvious b.Consider multiple approaches i.Top-to-bottom/bottom-to-top OSI model ii.Divide and conquer 3.Test theory to determine cause a.If confirmed, determine next steps b.If not confirmed, establish new theory or escalate The Troubleshooting Process (cont’d.)

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. 4.Establish a plan of action to resolve the problem and identify potential effects 5.Implement the solution or escalate as necessary 6.Verify full system functionality 7.Implement preventative measures, if applicable 8.Document findings, actions, and outcomes The Troubleshooting Process (cont’d.)

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. The true problem may be different from what the user tells you – The symptom may indicate a larger problem Identify the Problem

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Direct support – Observe what is or is not happening Phone support – Use closed-ended or open-ended questions Gather Information, Duplicate the Problem, Question Users, and Identify Symptoms

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Duplicate the problem – Can rule out user error as the cause Determine the scope of the problem – Are other users affected? Gather Information, Duplicate the Problem, Question Users, and Identify Symptoms (cont’d.)

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Example questions to users – “What was happening when the problem occurred?” – “Has anything changed on the system recently?” – “Has the system been moved recently?” Check your documentation – Includes system and hardware logs Determine If Anything Has Changed

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Break down complicated problems into manageable pieces – Methodically tackle each sub-problem Approach Multiple Problems Individually

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Based on experience Select the most probable cause from a list of all possible causes Question the obvious – Example: check to ensure a printer is powered on Considering multiple approaches can help avoid becoming locked in to a single approach Establish a Theory of Probable Cause

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. User cannot access the server – Opens database program and clicks on a recent document – The document does not open Consider a top-to-bottom or bottom-to-top OSI model approach – Application layer: consider whether a problem with the API is the possible cause Example Scenario

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Presentation layer: consider encryption between the application and database server Session layer: consider whether a port on the server is blocked Transport layer: consider the effect of extreme traffic Network layer: consider whether the IP address of the database server has changed OSI Model Approach

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Data link layer: consider whether the MAC address of the user’s machine or the database server is blacklisted Physical layer: check for a disconnected cable or a bad NIC OSI Model Approach (cont’d.)

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Reverse the approach using the OSI model beginning with Layers 1 and 2 Divide and conquer approach – Choose the OSI layer starting point based on a general sense of where the problem lies – If this starting layer is not the problem, move up or down the OSI model with new theories of probable cause Other Options for Tackling Multiple Options

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Test the theory without changing anything – You may not have permission to make the fix – The fix may have unanticipated repercussions Escalate the problem – Inform other parties for guidance – Pass the job to another authority with control over the device or issue Test the Theory to Determine Cause

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Write down the steps of your action plan Identify the potential effects of the actions Establish a Plan of Action and Identify Potential Effects

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Examples of implementation – Give advice to a user over the phone – Install a replacement part – Add a software patch Try only one solution at a time Document what you do Test the solution Implement the Solution or Escalate as Necessary

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. In the example scenario: – Have the user open the database while you are still at the computer Implement preventative measures to avoid a repeat of the problem – May involve educating the user to do or not do something Verify Full System Functionality and Implement Preventative Measures

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Purpose of documentation – Creates a knowledge database for future reference Eliminates duplication of work – Allows tracking problem trends Anticipate future workloads May identify less reliable brands or models Document Findings, Actions, and Outcomes

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Basic categories of network issues – Fixing problems at a user’s workstation, work area, or a server – Connecting to resources on the LAN Or WAN, but these may need to be escalated Stumbling block – Observed symptom may be the same for a variety of root causes Resolving Common Network Issues

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Example scenario – Everyone has local and Internet Web site access – The firewall configuration was recently changed Technician’s theories – The remote server is down – The remote site is inaccessible – The local firewall is preventing communication “We Can’t Access Our Web Server in Istanbul!”

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Quickest to test approach – Confirm all local office workstations cannot reach the remote server Using different hosts, try ping and ping6 utilities Traceroute shows functional path to the router, but no server response Run the mtr utility from a Linux box and simultaneously run pathping on a Windows system – Call the remote site to ask about the status “We Can’t Access Our Web Server in Istanbul!” (cont’d.)

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Determine whether the site is reachable from outside the local office – Would confirm or eliminate the theory of a local firewall configuration issue – Using a looking glass site tool, perform a ping test No pings receive a response from the server in question Other servers at the remote site do respond Conclusion: the remote server is down “We Can’t Access Our Web Server in Istanbul!” (cont’d.)

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Possible causes of an unresponsive server – Local power outage or blown circuit breaker – Failed NIC on the server – Network cable disconnected – Improper network configuration on the server – A changed patch cable location in the rack – Failed component in the server – Server shutdown “We Can’t Access Our Web Server in Istanbul!” (cont’d.)

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Problems you can fix at the workstation, work area, or server – Include physical and configuration problems Possible causes of an unreachable network device – Power failure or power anomalies – Hardware failure Hands-On Problems

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. EMI or RFI disrupting signals on copper cable Interface errors, such as improper wall jack installation Incorrect termination Cable to the workstation might be bad – Crossover versus straight-through cable Possible Causes of Unreachable Network Device

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Incorrect IP configuration Incorrect default gateway IP address information Out of date DNS entry Simultaneous wireless/wired connections – Can create a network failure Other Types of Hands-On Problems

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Figure 21.9 TCP/IP settings in Windows Server

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Figure Network Connections Advanced Settings

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Issues can arise when duplicating machines and using static IP addresses – A solution is to change the IP address on the new machine to an unused static IP or to DHCP LAN Problems

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Misconfigured DHCP settings – On a host: effect is limited to that host – On a DHCP server: many more machines affected Misconfigured DNS settings – On a DNS server: the server might direct hosts to incorrect sites or no sites at all – On a client: name resolution stops and the user experiences a downed network Server Misconfigurations

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Clues to server misconfiguration – Success in pinging a file server by address but not by name ► points to a DNS issue – Failure to discover neighboring devices/nodes ► may point to DHCP or DNS misconfiguration To fix misconfiguration – Go into the network configuration for the client or the server and look for problems Server Misconfigurations (cont’d.)

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Example: Figure – Bill intended to assign 6 ports to each VLAN Instead assigned 7 ports to VLAN 1 and 5 ports to VLAN 2 – Result: interface misconfiguration producing an incorrect VLAN assignment Patch cable placement errors can also occur – Keep proper records of patch cable assignments Adding VLANs

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Figure Bill’s VLAN assignments

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Scaling an Ethernet network – Bandwidth issues: one choice is to upgrade the switch and server NIC to the next higher Ethernet standard – Other approach: link aggregation or NIC teaming Protocols – Link Aggregation Control Protocol (LACP) – Cisco’s Port Aggregation Protocol (PAgP) Link Aggregation Problems

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Enabling LACP – Need two or more interconnected network interfaces configured for LACP – Devices communicate over multiple ports at the same speeds and form a single logical port Link Aggregation Problems (cont’d.)

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Figure LACP

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Active ports – Default to using LACP, if possible Passive ports – Wait for active ports to initiate conversation Common network error with LACP setups – Both sides of the connection set to passive ► an example of NIC teaming misconfiguration Link Aggregation Problems (cont’d.)

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Possible origination points – Local machines – LAN switches – Routers that interconnect the WAN – Switches within the distant network – Distant machines WAN Problems

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Nonfunctioning connections between networks Potential causes – Physical problems with the router or router interface modules – Loss of power – Problems with the Access Control List A misconfiguration can lead to missing IP routes Router Problems

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Key tool for determining a router problem beyond the local LAN is traceroute Run traceroute to the default gateway – A failed traceroute indicates a local issue – If the traceroute comes back positive, run it to an Internet site Router Problems (cont’d.)

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Figure Good connection

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. MTU mismatch – A network’s packets are so large that they must be fragmented to fit into the ISP’s packets Ways to remedy MTU mismatch – Techs can tweak the MTU settings to improve throughput – Path MTU Discovery (PMTU) determines the best MTU setting automatically PMTU runs under ICMP ISPs and MTUs

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Network appliances – Complex boxes with multiple features, e.g., routing, NAT, switching, IDS, firewall, and more NAT rules take precedence over appliance’s routing table entries – Tech must set the NAT rule order correctly Fix a NAT interface misconfiguration by setting up the network appliance correctly Appliance Problems

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Example – Amount of traffic between two company locations on a dedicated connection is causing huge bandwidth issues – Cause: sales department is sending large video files – Need to limit bandwidth for a single department – Need a blocking policy to enforce the limit – Need a company fair use policy to state limits Company Security Policy

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Problems to escalate – Problem that exceeds the tech’s skill level – Problem that involves third-party equipment Large organizations typically have clear escalation procedures CompTIA-recognized escalation situations – Broadcast storms, switching loops, routing problems, routing loops, and proxy ARP Beyond Local—Escalate

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Result of one or more devices sending nonstop broadcast frames onto the network Symptom: every computer on the broadcast domain cannot connect to network – Many users contact you simultaneously – Call a supervisor to get support Isolate devices until the problem device is identified Broadcast Storms

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Multiple switches inadvertently connected together to form a loop – Also called bridging loops Symptoms are identical to a broadcast storm Rarely take place on a well-running network – Most switches use the Spanning Tree Protocol Escalate the problem to discover the person making switch changes Switching Loops

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Occur when interconnected routers loop traffic Cause routers to respond slowly or not at all Clue: a huge amount of traffic—far more than the usual traffic—on the links between the routers Routing Loops

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Process of making remotely connected computers act as if they are on local LAN – VPN is the classic example Almost all proxy ARP problems involve the VPN concentrator – With misconfigured proxy ARP settings, the VPN concentrator sends what looks like a DoS attack on the LAN Proxy ARP

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. End-to-end principle – Applications and work should happen only at endpoints in a network – The Internet was founded on this principle Modern networks – Much activity happens at intermediate devices reflects the current state of the Internet End-to-End Connectivity

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Connecting users with essential resources within a smaller network, e.g., aLAN or a private WAN – A tech’s job includes ensuring connections happen fully End-to-End Connectivity (cont’d.)

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Apply good troubleshooting methodology Constantly increase your network knowledge Become a troubleshooting artist – Benefit: Easier to deal with a network disaster Troubleshooting Is Fun!

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Everyday objects capable of communicating with each other A large-scale idea – Changes promised by IoT – Challenges involved with IoT – Technologies making IoT possible Internet of Things (IoT)

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Vast array of real-world smart objects – Collecting sensor data – Communicating that data with other objects or computers – Making decisions based on it Examples of smart objects in the home and at the gym Larger scale applications, e.g., the power grid Utopia of things

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. Bugs Hacking Feedback loops Interoperability Waste and obsolescence Power Scale Challenges?

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. IPv6 is essential for enough address space Ultra-low-power wireless radios – Communications with vast networks of sensors IEEE is a hybrid networking standard – MoCA provides Ethernet access through existing coaxial cabling – HomePlug (IEEE 1901) provides high-speed home networking—Ethernet over power (EoP) Supporting Technologies

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. nVoy: the branding for IEEE nVoy-certified networking equipment: – Will create a single network for devices spread across Ethernet, Wi-Fi, MoCA, and HomePlug connections – Can make intelligent decisions when communicating with devices that use more than one connection type Supporting Technologies (cont’d.)

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Fourth Edition (Exam N ) Copyright © 2015 by McGraw-Hill Education. All rights reserved. There is no clear finish line to mark the arrival of IoT – The networking requirements leading to IoT will be incremental One day communications between smart devices may overtake the traffic generated by human users Looking Ahead