Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Network Troubleshooting Chapter 20

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Objectives Describe appropriate troubleshooting tools and their functions Analyze and discuss the troubleshooting process Tackle a variety of troubleshooting scenarios

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Overview

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Introduction to network troubleshooting

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Three parts to Chapter 20 Troubleshooting tools The troubleshooting process Troubleshooting scenarios

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Troubleshooting tools

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Hardware tools –Cable tester, TDR, and OTDR –Certifiers –Voltage event recorder/temperature monitor –Protocol analyzer –Cable stripper/snips –Multimeter –Tone probe and tone generator –Butt set –Punchdown tool

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Hardware tools (cont.) –Cable testers, TDRs, and OTDRs Devices to test for broken cables –Cable testers »Continuity problems and wire map –TDRs (time domain reflectometers) »Locates copper cable breaks –OTDRs »Locates fiber-optic cable breaks

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Figure 20.1 Typical cable tester

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Figure 20.2 An EXFO AXS-100 OTDR (photo courtesy of EXFO)

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Certifiers –Only use for slowdowns, not disconnects –Require a loopback on the far end –Ensure a cable can handle its rated capacity –Problems that reduce cable capacity Crosstalk Attenuation Interference

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Voltage event recorder/temperature monitor –Detect power and heat problems –Cause intermittent problems –Heat problems in server rooms –Monitor power with voltage event recorder –Monitor temperature with temperature monitor

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Protocol analyzers –Monitor protocols at different layers Application, Session, Transport, Network, Data Link –Both hardware and software tools

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. When to use a protocol analyzer –You need to see data to analyze the problem 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 traffic is slowing down the network

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Cable stripper or snip –Enable you to make UTP cables –Also need crimpers –Often combined in one tool

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Figure 20.3 A cable stripping and crimping tool

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Multimeters –Test AC and DC voltage –Test resistance –Test continuity –A great fallback when you do not have a cable tester

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Tone probes and tone generators –Work together to identify opposite ends of unlabeled cable runs –Tone generator puts a signal (tone) on wire –Tone probe on opposite end detects the signal

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Butt sets –Hand set –Use to tap into a 66- or 110-block to test a line

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Punchdown tools –Put UTP wires into 66- and 110-blocks –Repunch a connection to make sure contacts are set

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Figure 20.4 A punchdown tool in action

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Software tools –Built-in commands and utilities: otracert/traceroute oipconfig/ifconfig oping and arping onslookup/dig ohostname omtr oroute onbtstat onetstat –Packet sniffer –Port scanners

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. tracert/traceroute –Traces all routers between two points –Use to discover where a problem lies –Problem is just beyond the last router displayed before error –Some routers block traceroute packets

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. 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 [ ] Listing 20-1 Sample traceroute output

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. ipconfig/ifconfig –Displays IP settings –ipconfig without parameters Basic information only –ipconfig /all gives configuration details

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. 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. : Listing 20-2 Sample ipconfig output

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. eth0 Link encap:Ethernet HWaddr 00:02:b3:8a:7d:ae inet addr: Bcast: Mask: inet6 addr: 2001:470:bf88:1:202:b3ff:fe8a:7dae/64 Scope:Global inet6 addr: fe80::202:b3ff:fe8a:7dae/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets: errors:0 dropped:0 overruns:0 frame:0 TX packets: errors:0 dropped:0 overruns:0 carriers:0 collisions:0 txqueuelen:1000 RX bytes: (292.5 MB) TX bytes: (132.9 MB) lo Link encap:Local Loopback inet addr: Mask: inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:15414 errors:0 dropped:0 overruns:0 frame:0 TX packets:15414 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes: (1.0 MB) TX bytes: (1.0 MB) Listing 20-3 Sample ifconfig output

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. ping –Queries by name or IP address –Uses ICMP packets –Works across routers –Problem: devices can block ICMP

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. 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 Listing 20-4 Sample ping output

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. arping –Queries by IP address –Uses ARP frames –Problem: does not cross routers –Only on UNIX and UNIX-like systems

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. 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 Listing 20-5 Sample arping output

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. nslookup/dig –Both diagnose DNS problems –nslookup (all operating systems) Poor tool – considered obsolete Without switches, provides name and IP address of default DNS server –dig – more powerful Every OS but Windows

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. dig mx totalsem.com ; > 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. Listing 20-6 The dig command Listing 20-7 Output for the dig command

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. hostname –Simplest of all utilities –Returns name of host from which it runs –hostname sample output c:\> c:\>hostname Mike-win7beta

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. My Traceroute (mtr) –Dynamic (keeps running) –Equivalent to traceroute –Not available in Windows

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. 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% Listing 20-9 Sample mtr output

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. route –Display and edit local routing table –Type route print

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. 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 Listing Sample route print output

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. nbtstat –Windows (all versions) only –Command-line equivalent of My Network Places –Must use a switch –nbtstat –n shows local NetBIOS names

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. 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 Listing Sample nbtstat output

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. netstat –Shows 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 routing table (like route print )

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. 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 Listing Sample netstat output

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Packet sniffer –A.k.a. protocol analyzer or packet analyzer –Intercepts and logs network packets –Many choices –Software example: Wireshark –Dedicated hardware devices

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Figure 20.5 Wireshark in action

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Port scanners –Probes remote system’s ports –Logs state of scanned ports –Good use: find unintentionally opened ports in order to close –Bad use: find open ports and use to break in –nmap runs on UNIX and Windows –Angry IP Scanner for Windows

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Figure 20.6 Angry IP Scanner

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Throughput testers –Enable you to measure the data flow in a network –Which tool to use depends on what part of network you want to test –Several speed-testing Web sites available for checking an Internet connection’s throughput

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Figure 20.7 Speed test results from Speakeasy

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. The troubleshooting process

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Memorize these problem analysis steps: Identify the problem –Gather information –Identify symptoms –Question users –Determine if anything has changed Establish a theory of probable cause –Question the obvious

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Memorize these problem analysis steps (cont.): Test the theory to determine cause –Once theory is confirmed, determine next steps to resolve problem –If theory is not confirmed, re-establish new theory or escalate Create an action plan and solution identifying potential effects

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Memorize these problem analysis steps (cont.): Implement and test the solution and escalate as necessary Verify full system functionality and, if applicable, implement preventative measures Document findings, actions, and outcomes

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Troubleshooting scenarios

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Troubleshooting scenario one –“I can’t log in!” Biggest and most complex scenario Log in from other machines Attempt to log in yourself and try to ping Use ipconfig or ifconfig

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Troubleshooting scenario two –“I can’t get to this Web site!” Have user try to reach another Web site Try to ping the site by name and IP address Determine whether DNS is functioning Ping the gateway or proxy server Ping other sites If other sites reachable, notify problem site owner If no sites available, notify your ISP

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Troubleshooting scenario three –“Our Web server is sluggish!” Connect from another location If connection is also slow, problem with server Check server logs for changes Run Performance Monitor and compare new logs with previously established baseline logs If connection from other location OK, run tracert command from user’s computer to reveal slow hop

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Troubleshooting scenario four –“I can’t see anything on the network!” Check connectivity Ping a remote system Ping loopback address –If error, run ipconfig /all and fix settings –If no error, check hardware »Run utility on NIC »Test cable

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. It’s time to escalate! –Broadcast storms –Switching (bridging) loops –Route problems –Routing loops –Proxy ARP

Mike Meyers’ CompTIA Network+ ® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N ) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Troubleshooting is fun! –Apply good troubleshooting methodology –Constantly increase your knowledge –Become a troubleshooting artist