Network+ Objective 5.2 - Network Troubleshooting Tools

ping

A LINUX/DOS command that tests connectivity and isolates hardware problems and any mismatched configurations. • ping <IPADDR> - Test reachability an IP address • ping -t <IPADDR> - Ping until stopped with Ctrl-c • ping -a <IPADDR> - Resolve address to a hostname • ping -n <count> <IPADDR> - Send # of echo requests • ping -f <IPADDR> - Send with Don't Fragment flag set

pathping

A TCP / IP command that is a combination of ping and traceroute. It provides information about latency and packet loss on a network.

ifconfig

A TCP/IP configuration and management utility used with UNIX and Linux systems to display the network interface configuration.

netstat

A TCP/IP troubleshooting utility that displays statistics and the state of current TCP/IP connections. It also displays ports, which can signal whether services are using the correct ports. • netstat -a - Show all active connections • netstat -b - Show binaries • netstat -n - Do not resolve names

Packet sniffer

A device or program that monitors the data traveling between computers on a network.

Light meter

A device to measure light intensity

Nmap

A network utility designed to scan a network and create a map of network devices. Frequently used as a vulnerability scanner. Can detect devices, ports, operating systems, running services.

OTDR (Optical Time-Domain Reflectometer)

A performance testing device for use with fiber-optic networks. An OTDR works by issuing a light-based signal on a fiber-optic cable and measuring the way in which the signal bounces back (or reflects) to the OTDR. Based on the type of return light signal, an OTDR can accurately measure the length of the fiber; determine the location of faulty splices, breaks, bad or mismatched connectors, or bends; and measure attenuation over the cable.

cable crimper

A tool used to attach a connector onto the end of a cable, causing the internal RJ-45 pins to pierce the insulation of the wires, thus creating contact between the conductors at each wire.

Punchdown tool

A tool used to punch individual wires from a network cable into their slots, in a terminal block (66/110), to terminate the cable.

Cable tester

A tool used to test a cable to find out if it is good or to find out what type of cable it is if the cable is not labeled.

Protocol analyzer

A type of diagnostic software that can examine and display data packets that are being transmitted over a network. Also called a network analyzer.

Port scanner

A type of software that searches a network host for open ports.

arp

Address Resolution Protocol. Resolves/displays the ARP table (IP addresses to MAC addresses). The arp command can also be used to add entries to the arp table (arp -s).

Multimeter

An instrument for measuring the properties of an electrical circuit, such as voltage and current, and continuity.

tcpdump

Capture packets from the command line. Available in most Unix/Linux operating systems. Included with Mac OS X, available for Windows (WinDump). Apply filters, view in real-time. Written in standard pcap format.

nslookup

Command-line program in LINUX/Windows used to determine exactly what information the DNS server is providing about a specific host name.

iptables

Linux iptables (firewall) - filter packets in the kernel • Simple data blocks - ignores state • Usually placed on a device or server

Tone generator and probe

Puts an analog signal on the wire. An inductive probe doesn't need to touch the copper/wire to detect the signal. Useful for mapping and testing cables.

WiFi analyzer

Tool for checking/diagnosing issues on a wireless network.

tracert, traceroute

Traceroute is a computer network diagnostic tool, displaying the route and measuring transitdelays of packets across the network. The command is available in Unix OS as 'traceroute', while it is available as 'tracert' in Windows NT based OS. For IPv6 it is often known as 'tracert6' • Takes advantage of ICMP Time to Live Exceeded error message • Not all devices will reply with ICMP Time Exceeded messages

Loopback adapter

Useful for testing physical ports (serial, Ethernet, T1, fiber). These are not crossover cables. Plugs into a port and crosses over the transmit line to the receive line so that outgoing signals can be redirected into the computer for testing.

Spectrum analyzer

Useful for viewing the spectrum usage of wireless devices. For survey or interference monitoring.

Bandwidth speed tester

Usually a web site which will test your network speed by upload and downloading a large file. Performance can be affected by many factors, including the website being used for the test.

route

View the device's routing table (WIN & LIN) • route print - View the Windows routing table

ipconfig

Windows command that shows the IP configuration settings on a PC • ipconfig - Windows TCP/IP config • ipconfig /all - Display all IP configuration details • ipconfig /release - Release the DHCP lease • ipconfig /renew - Renew the DHCP lease • ipconfig /flushdns - Flush the DNS resolver cache • ifconfig - Linux interface configuration

dig

dig (domain information groper) is a network administration command-line tool for querying the DNS. dig is useful for network troubleshooting and for educational purposes. It is used to determine exactly what information the DNS server is providing about a specific host name.