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about the changes that have been made recently. However, sometimes changes aren’t under your control or you’re oblivious to them. Good examples of this include browser updates, plug-ins, and virus protection patterns. Therefore, when the change is not obvious, you have to stop banging your head against the wall and get back down to basics. For example, let’s say everybody in your office starts having problems shutting down. They all get stuck at the “Please wait while your computer shuts down” screen. It seems, at first glance, that everybody is going to have to deal with it. Nobody has changed anything recently that they know of, and no one is capable of wading through the guts of what’s going on. Even though this doesn’t seem like a network problem, the fact that it just started spontaneously on a bunch of networked computers seems very odd, so it gets dumped in your lap. Fortunately, you realize that even if social engineering does not reveal the source of the change, something has changed, and you can at least use the divide-and-conquer method to figure out what it is. Because your office runs Windows 95, many of the programs that run at startup are in the Startup menu. You get rid of everything in the Startup menu and reboot. All of a sudden, you can shut down again. You return half of the programs to the Startup folder and keep restarting until you find the source of the problem. It turns out to be your email notification program. However, you decide to start up with just the email notification problem, and you’re able to shut down. In this case, you’ve got an interaction problem, which is further solvable via the divide-and-conquer method. You put back in half of the programs that were in the startup file, and you manage to track the problem down to a situation where you have both the virus protection program and the email notification program loaded. As you might have guessed, this troubleshooting session actually happened to me—the virus protection program, which is automatically updated from the Internet, had started to interfere with the email notification program. A quick search of the vendor’s Web site found a patch for the email client (not the virus protection program) and an annoying problem was fixed. Obviously, the divide-and-conquer method doesn’t always work to ultimately solve your problems. In particular, it’s tough to troubleshoot intermittent problems, as well as quantitative (rather than qualitative) problems that don’t involve a black-and-white (broken or not broken) scenario. You can remember the difference between qualitative and quantitative by keeping in mind that qualitative is the analysis of the quality of a situation (as in, “My workstation cannot print at all”). Quantitative refers to the analysis of the quantity involved with a situation (as in, “My workstation is slower at printing than Sally’s”). For example, the divide-and-conquer method might lead you to believe that a new application is causing your network slowdowns (and you might be right). However, it’s not always feasible to get rid of a new application, and, furthermore, it might not be clear whether the trouble is this particular application or
just that the network itself is at a saturation point in general. In this case, you might try a different application, but can you really switch a largely deployed application in a short period of time? You’ll probably just end up checking the application to see if it’s misconfigured and taking measurements to ensure that the application is behaving properly on your network. The bottom line is this: Even when the divide-and-conquer method can’t directly find your problem, it can at least point you in the right direction. Previous Table of Contents Next
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To access the contents, click the c
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Workshop Q&A Quiz Answers to Quiz Q
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Eminent Domain TCP/IP Graffiti DHCP
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Configuring Your Proxy Proxy Troubl
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Socks Stuff AOL Instant Messenger A
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Table of Contents Introduction: Get
Page 13 and 14: about your more complex network iss
Page 15 and 16: Tell Us What You Think! Table of Co
Page 17 and 18: with me when I was first getting st
Page 19 and 20: NIC (network interface card) The te
Page 21 and 22: MAC Attack Previous Table of Conten
Page 23 and 24: Routers Previous Table of Contents
Page 25 and 26: technology as the future of local a
Page 27 and 28: for a TCP/IP address in a large net
Page 29 and 30: Sprechen Sie DLC? Previous Table of
Page 31 and 32: socket 80 of the TCP/IP address 167
Page 33 and 34: program in a name entry; entering t
Page 35 and 36: WINS Previous Table of Contents Nex
Page 37 and 38: kind and spit them out as fast as p
Page 39 and 40: Previous Table of Contents Next Hou
Page 41 and 42: Figure 2.1 A simple logical map. If
Page 43 and 44: Figure 2.4 A physical documentation
Page 45 and 46: the room). This way, you can read t
Page 47 and 48: un on the server at 9:50 on Monday
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Page 51 and 52: Beware of Vendor Your vendor probab
Page 53 and 54: call the risk/benefit ratio—the a
Page 55 and 56: Workshop Q&A Previous Table of Cont
Page 59 and 60: If you determine that it’s just o
Page 61 and 62: (see Figure 4.2). Figure 4.2 An Eth
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Page 67 and 68: A Each situation is obviously diffe
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Page 73 and 74: Drive duplication can be a big help
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Page 77 and 78: 5. When you log problems on a given
Page 79 and 80: if they have a plan, they are going
Page 81 and 82: Is It a Virus, Doc? Previous Table
Page 83 and 84: O: Only have tried two other Intern
Page 85 and 86: A Remember that what a user says is
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Page 91 and 92: Figure 7.1 Searching several sites
Page 93 and 94: You’ll also find forums run by th
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Page 97 and 98: a server but you think it should be
Page 99 and 100: Workshop Q&A Previous Table of Cont
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Page 103 and 104: Name Brand Versus Generic PCs The c
Page 105 and 106: static electricity that may have bu
Page 107 and 108: SIMMs and DIMMs There are two kinds
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Page 111 and 112: This is called looping back, becaus
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Figure 8.4 The NT Task Manager’s
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UNIX Previous Table of Contents Nex
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Probably the most important thing t
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Hour 9 Ethernet Basics Previous Tab
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which translates into lots of colli
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it currently requires fiber-optic c
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designation is simply an industry-s
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Down, Down, Down Previous Table of
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A Collisions cause other errors, su
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Follow the Rules: Share and Enjoy!
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Previous Table of Contents Next Err
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Token Analyzers Finding a NAUN is r
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Token-Ring does not have any hard-a
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Down Town Previous Table of Content
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C. 1, 16 D. 4, 16 Answers to Quiz Q
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Going Native Although Windows allow
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Eminent Domain Previous Table of Co
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machine with the username Administr
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protocol. They therefore relied on
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Previous Table of Contents Next Fol
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Most of the time, you’ll not want
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allows you to manage them and check
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Binding Previous Table of Contents
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Figure 11.6 Showing bindings for al
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Informational Commands Previous Tab
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Figure 11.8 A monitor session. We k
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case you need them. 2. What does SM
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a great example of client/server. W
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Previous Table of Contents Next Alt
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The first number is the process ID
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tcp 0 0 frotz.frob.com.telnet 200.1
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Name Game Previous Table of Content
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The next thing you need to find out
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A UNIX security and file permission
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Previous Table of Contents Next Hou
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the amount of time used or data sen
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NLMs In addition to accepting comma
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NLM Party Previous Table of Content
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Again, make sure you are running th
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Big Monitor Is Watching Previous Ta
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Then, eureka! During one session of
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Protocol Problems Previous Table of
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Figure 13.10 UNICON will configure
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Summary Previous Table of Contents
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7. The TCP/IP protocol and basic se
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ivory-tower stuff, but some of it i
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Configuring in Comfort Previous Tab
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Router 1 in Figure 14.3 is shown in
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to that network. Instead, the next
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Route in Peace: Routing Protocols P
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get to a network segment that until
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Figure 14.4 How two stations talk v
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Tree Trunks Previous Table of Conte
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garbage characters like these on a
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A. Add Router 99 to Router 88’s r
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Let’s lay out some definitions he
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Packet-Filtering Routers Previous T
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eceptionist hangs up one line (the
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from the proxy server without causi
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Proxy Trouble Previous Table of Con
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3. The proxy server resolves the na
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Q My vendor says that its firewall
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Previous Table of Contents Next Par
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• Make checklists of tasks that m
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Joe User Previous Table of Contents
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groups | grep -q -w network && { ec
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If you’re going to add or replace
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Policies Previous Table of Contents
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in this hour—will pay off as you
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Q Which duplication software is rig
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Hour 17 Where Do I Start? Previous
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As optimistic as we’d all like to
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• PCAnywhere • ReachOut • Rem
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IPX/SPX Previous Table of Contents
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Q What happens if I ping the loopba
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correlations? A. netstat -a B. trac
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equire that the application files t
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The File and Print Blues Previous T
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With five potential points of failu
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In some cases, a slight difference
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Application Celebration Previous Ta
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Proto Local Address Foreign Address
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printer 515 Line Printer Daemon (ne
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Previous Table of Contents Next
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Connected to 167.195.160.6. Escape
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Workshop Q&A Q What in the blazes i
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3. A 4. B 5. False 6. B 7. True 8.
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Intranet = Internal The word intran
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Internet Identification Previous Ta
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If an outside machine is “on the
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Here I Ping Again Previous Table of
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Figure 19.6 DNS zones, like the fol
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[rs.internic.net] Registrant: John
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For example, I ran an NFS server on
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• SMTP—Simple Mail Transfer Pro
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Dialout DNS Previous Table of Conte
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3. What does DMZ stand for? A. DNS
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• It’s a way to avoid a Dilbert
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Socks Stuff Previous Table of Conte
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Figure 20.2 The AOL Instant Messeng
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RealPlayer Previous Table of Conten
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external client for proxy support,
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Typical Operation Previous Table of
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scantily, and still others are not
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Not every kind of filter is availab
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important. Your relative or interpa
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Application Antics Previous Table o
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Broken Ring Previous Table of Conte
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creating a segment between the swit
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Q Where can I get an Ethernet mini-
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Figure 22.1 The MG-Soft MIB browser
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the probe has picked up what’s go
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Previous Table of Contents Next Her
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information without the overhead th
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A. Broadcast B. Baseline C. Brag D.
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• Application efficiency • Serv
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Application and Protocol Efficiency
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and so on—is to measure. Everythi
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it a point to say, “Would you sho
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Here are the two types of performan
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Network Statistics Previous Table o
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Q About that latency analysis metho
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Router Configuration Previous Table
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For the second option, you’ll hav
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Automatic for the People Previous T
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are in an unknown location) to conn
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Previous Table of Contents Next The
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C. SYS:SYSTEM\AUTOEXEC.BAT D. SYS:P
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active hub An active hub is one tha
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A TCP-based authentication service
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applications and protocols are base
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An extremely fast network cable tha
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See Internet Group Management Proto
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A device that converts (modulates)
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providers. Point-to-Point Tunneling
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security audit An examination (ofte
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An essential part of a network inte
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Index Symbols A 100 Megabit Etherne
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C new product, 45-46 burned-in addr
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DLC (Data Link Control), 17 DMZ (de
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F fat finger factor, 42-43, 46 fata
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ICQ, 335-336 IMAP (Internet Mail Ap
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M filters, 347-352 LANDecoder, 347
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NetBIOS (Network Basic Input/Output
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network card. See NIC Network Contr
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power supply check, 66 troubleshoot
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Q-R qualitative problems, 58 quanti
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names, 393-394 NetWare, 202 paging
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T dumb terminal mode, 211, 224 full
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isolating soft errors, 135-136 LANa
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U standardizing configuration, 245
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V W upstream, 134 Usenet newsgroups
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autodetection problems, 159 broadca
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