Key Terms
arping A UNIX command used in place of ping to see if you can reach a remote computer. It uses Address Resolution Protocol (ARP) packets rather than the ICMP packets used by ping (that are blocked or ignored by many devices). Not available on Windows systems, arpingframes do not cross routers.
broadcast storm A nonstop flurry of broadcast frames on the network that can keep computers on the broadcast domain from connecting to the rest of the network.
butt set A special handset used to tap into a 66- or 110-block to see if a particular line is working.
cable stripper A device that enables you to make UTP cables by stripping the cover off cable before using a crimper to attach crimps (connectors) to the cable ends.
cable tester A device that will reveal continuity problems caused by a broken cable.
certifier A device that tests a cable to ensure that it can handle its rated capacity. Use a certifier for slowdowns, not disconnects.
dig A command used to diagnose DNS problems;however, it is not available on Windows.
hardware tool In the context of network troubleshooting, a device dedicated to the purpose of performing one or more tests on a network.
hostname A command that simply returns the host name of the local computer.
ifconfig The command used in operating systems other than Windows that gives you information about a computer’s IP settings. The /all switch gives additional detailed information, including DNS server addresses and MAC addresses.
ipconfig The Windows version of the ipconfig command.
multimeter A device that tests voltage, resistance, and continuity on a line.
My traceroute (mtr) A command that is similar to traceroute except that it keeps running until shut down. Not available in Windows.
nbtstat A Windows command that shows all the local NetBIOS names and is a command-line equivalent to My Network Places. You must run nbtstat with a switch.
netstat A command-line utility that displays information on the current state of all the running IP processes on your computer. Use netstat when you want to know about your current sessions.
nslookup A command used to diagnose DNS problems, but considered obsolete. The digcommand is a more powerful alternative but is not available on Windows
packet sniffer A software utility or dedicated hardware device that intercepts and logs network packets. Wireshark is a popular packet sniffer.
ping A command that uses Internet Control Message Protocol (ICMP) packets to query by IP or by name, and which works across routers. Usually it is the first tool used to check if a system is reachable.
port scanner Software that probes ports on another system, logging the state of scanned ports. You can use it to find an unintentionally open port so it can be secured. Hackers like to use port scanners to find vulnerabilities in other systems
protocol analyzer Specialized software or hardware used to view the Application, Session, Transport, Network, and Data Link layer information on every frame going through your network.
proxy ARP The process of making remotely connected computers truly act as though they are on the same LAN as local computers. Proxy ARPs are done in a number of different ways, such as with a Virtual Private Network (VPN).
punchdown tool A device that places UTP wires into 66- and 110-blocks. It is useful in a diagnostic environment to repunch a connection to make sure all the contacts are properly set.
route A command-line command that enables you to display and edit the local system’s routing table.
routing loop Something that occurs when interconnected routers loop traffic, causing the routers to respond slowly or not respond at all. Dynamic routing protocols sometimes cause routing loops when a router goes down, but static routes usually cause routing loops.
snip Another term for cable stripper. See cable stripper.
switching loop A traffic loop, resulting in every computer on the broadcast domain being unable to access the network. Caused by the way in which multiple switches are connected, but normally avoided by switches using the spanning tree protocol.
temperature monitor When experiencing intermittent network problems, use a temperature monitor to ensure proper temperature.
tone generator When cabling is improperly labeled, a tone generator and tone probe are used to locate the two ends of each cable. The tone generator is a device that sends a signal, called a tone, over a cable. It is paired with another device, called a tone probe, which you place on the ends of cables until it detects the tone, identifying the other end of the cable.
tone probe A device that is used with a tone generator to identify the ends of cables that are not properly labeled.
traceroute A command-line utility used to trace all the routers between two points. Use it to diagnose problems reaching a remote system. Many routers block tracert packets; therefore, tracerouteis a viable alternative.
tracert The Windows version of traceroute.
voltage event recorder When experiencing intermittent network problems use a voltage event recorder to measure power.
Wireshark Popular free packet sniffing software available at
compatibility issue An issue that may affect how existing equipment, applications, or cabling work together.
external connection A connection outside of your network, including connections to the Internet or other networks not under your control.
high-speed WAN interface card (HSWIC) Router expansion card that allows you to add additional ports, usually to connect ISPs or other high-speed connections.
internal connection A connections within and controlled by your network.
lights-out management (LOM) Management software built into higher-end servers that allows server management and control even when the server is turned off.
list of requirements Defines the network’s requirements, such as security, cabling, devices, and so forth.
MTU black hole Condition where network devices, such as routers and firewalls, block ICMP, preventing MTU discovery.
MTU mismatch Condition where your network’s packets are so large that they must be fragmented to fit into your ISPs packets.
network design Determining and quantifying the equipment, operating systems, and applications used by the network.
Path MTU Discovery (PMTU) A new method to determine the best MTU settings automatically by adding the “Don’t Fragment (DF) flag” to the IP packet.
peripheral Equipment that connects to your network, such as networked printers, scanners, and fax machines.
security Providing mechanisms (such as firewalls, anti-malware, etc.) within your network design to assure the protection of information and systems.
Small Form-Factor Pluggable (SFP) Module used in networking equipment, such as switches, that allows different fiber connections from the device.