Network Troubleshooting and Tools (2) Flashcards
Which of the following Windows tools uses ICMP messages and manipulates IPv4 time-to-live values to illustrate the route packets take through an internetwork?
Ping
Route
Tracert
Tracert
The Windows tracert tool transmits a series of ICMP messages with incrementing time-to-live (TTL) values, which identify each router on the path the packets take through the network. ping uses ICMP, but it does not manipulate TTL values. netstat, route, and nslookup do not use ICMP messages, nor do they manipulate TTL values when performing their normal functions
Users are having trouble connecting to Internet hosts. Alice suspects that there is a problem with the Domain Name System (DNS) server, and she wants to verify this. Which of the following steps can she take to determine whether the DNS server is resolving Internet hostnames?
Issue the ipconfig command from a local workstation
Try to connect to a host using the Internet Protocol (IP) address instead of the hostname
Ping the DNS server to see if it is functioning
Try to connect to a host using the Internet Protocol (IP) address instead of the hostname
If Alice suspects that a DNS server isn’t resolving hostnames, she should try connecting to a remote host using the IP address instead of the name. If she can connect, she knows that all internal local area network (LAN) components and the Internet gateway are functioning, and the remote host is functioning. The problem most likely lies within the DNS server itself. If Alice can’t connect to a remote host using the IP address, the problem isn’t the DNS server. She would need to do more testing to isolate the problem device and the affected area. ipconfig is a workstation command that enables you to verify the local IP configuration; it isn’t used to test a DNS server’s functionality. Using the ping command will only tell you whether the computer hosting the DNS service is functioning at the network layer of the Open Systems Interconnection (OSI) model; it will not test the DNS service functionality. The tracert (or traceroute) command is used to identify the hop-by-hop path taken to reach a destination; it doesn’t allow you to test functionality above the network layer of the OSI model
Which of the following utilities can you use to view resource record information on a particular DNS server? (Choose all correct answers.)
netstat
nslookup
nbtstat
arp
dig
nslookup
dig
nslookup and dig are both command-line utilities that you can direct to a specific DNS server and then generate queries that display resource record information the program retrieves from the server. netstat displays information about networking protocols, whereas nbtstat displays information derived from the system’s NetBIOS over TCP/IP implementation. arp is a tool that you can use to display and manage a system’s ARP table entries. netstat, nbtstat, and arp are not able to display resource record information
Which of the following types of wiring faults cannot be detected by a wiremap tester?
Split pairs
Open circuits
Short circuits
Split pairs
A wiremap tester consists of a main unit that connects to all eight wires of a UTP cable at once and a loopback device that you connect to the other end, enabling you to test all of the wires at once. A wiremap tester can detect opens and shorts, as well as transposed wires. However, it cannot detect split pairs because, in that fault, the pins are properly connected
After connecting a tone generator to the green wire at one end of a twisted pair cable run, Ralph proceeds to the other end of the cable and touches the locator to each of the eight pins in turn. The green wire and the green striped wire both produce a tone. What type of wiring fault has Ralph discovered?
Far-end crosstalk
Transposed wires
Short circuit
Short circuit
The first and most essential test that installers must perform on every cable run is a continuity test, which ensures that each wire on both ends of the cable is connected to the correct pin and only the correct pin. If a pin on one end of a cable run is connected to two or more pins on the other end, you have a short circuit
Which of the following troubleshooting tools is not used to test copper cabling installations?
Wiremap tester
Multimeter
OTDR
OTDR
An optical time domain reflectometer (OTDR) is a device that transmits light pulses over a fiber-optic network and measures the time interval and strength of the returning pulse, to measure the length of the cable run. An OTDR can be used to locate fiber-optic cable breaks, as well as characterize a cable run’s reflectance, optical return loss, and other characteristics. Multimeters, tone generators, and wiremap testers are all devices that work only with copper networks
Ralph has been advised to check his Linux web servers for open ports that attackers might be able to use to penetrate the servers’ security. Which of the following utilities can Ralph use to do this?
tcpdump
iptables
nmap
nmap
The nmap utility is capable of scanning a system for open ports that might be a security hazard. The tcpdump, dig, and iptables utilities cannot do this
While performing a protocol analysis, Alice notes that there are many ICMP packets in her captured traffic samples. She attributes these to her frequent use of TCP/IP troubleshooting tools. Which of the following utilities are used to test network layer characteristics of a host using Internet Control Message Protocol (ICMP) messages? (Choose all correct answers.)
ipconfig
netstat
ping
tracert
ping
tracert
ping and tracert are both utilities that test network layer characteristics using ICMP messages. ping tests the network layer functionality of the host, and traceroute displays the path to the host through the internetwork. ipconfig and netstat do not use ICMP messages
Which of the following parameters enables you to specify the time-to-live (TTL) value of the messages ping transmits?
- n
- t
- i
-i
Running the ping tool with the -i parameter enables you to specify the time-to-live (TTL) value of the messages ping transmits. The -t parameter causes the ping tool to send messages to the target continuously until you manually stop it. The -n parameter enables you to specify the number of messages the ping tool should transmit. The -a parameter resolves an IP address you specify as the target to a hostname
Which of the following command-line utilities is capable of performing the same basic function as traceroute or tracert?
ping
pathping
netstat
pathping
Like traceroute and tracert, pathping is capable of generating a list of the routers that packets pass through on the way to a specific destination system. pathping also displays the percentage of lost packets for each hop, which traceroute and tracert cannot do. The ping, netstat, and route utilities are not capable of displaying route traces
What is the name for a device that determines the length of a cable by transmitting a signal at one end and measuring how long it takes for a reflection of the signal to return from the other end?
Fox and hound tester
Wiremap tester
Time domain reflectometer
Time domain reflectometer
The technique that provides this capability is called time domain reflectometry (TDR). The tester transmits a signal over the cable and measures how long it takes for a reflection of the signal to return from the other end. Using this information and the cable’s nominal velocity of propagation (NVP)—a specification supplied by the cable manufacturer—the device can calculate the length of a cable run
Which TCP/IP utility should you use to most easily identify a malfunctioning router on your network?
ifconfig
ping
traceroute
traceroute
The traceroute (or tracert) utility can locate a malfunctioning router by using an Echo Request messages with incrementing TTL values. ifconfig is a network configuration utility for Unix and Linux systems; ping can test connectivity to another TCP/IP system, but it cannot locate a malfunctioning router; and netstat displays information about network connections and traffic but cannot locate a malfunctioning router
Which of the following protocols does the ping program never use to carry its messages?
IP
UDP
TCP
TCP
All Windows ping transactions use ICMP messages. ICMP messages are encapsulated directly within IP datagrams; they do not use transport layer protocols, such as UDP. Ping transactions to destinations on the local network are encapsulated within Ethernet frames. On Unix and Linux, ping uses UDP, which is also encapsulated in IP datagrams
Which of the following commands displays the routing table on the local computer?
arp –r
netstat –r
ifconfig –r
netstat –r
The netstat utility can display the routing table, along with other types of network traffic and port information. The arp utility is for adding addresses to the ARP cache; it cannot display the routing table. The ifconfig command displays TCP/IP configuration information on Unix and Linux systems; it cannot display the routing table. Telnet is a terminal emulation program; it cannot display the routing table
A routine test of a newly installed twisted pair cable run with a wiremap tester indicates that there is a short circuit on one of the wires. Which of the following procedures might possibly correct the fault?
Use a different pinout on both ends of the cable
Replace the connectors at both ends of the cable run
Move the cable away from any potential sources of electromagnetic interference
Replace the connectors at both ends of the cable run
A short circuit is a wiring fault indicating that a pin at one end of a cable run is connected to two pins at the other end. To correct the problem, you must replace the connector with the faulty wiring. None of the other suggestions are solutions for a wiring fault
