5.0 CompTIA Network troubleshooting and tools

All telnet operations are sent as how many bits?

8 bits

flow record

A flow record defines the information that NetFlow gathers , such as packets and the types of counters gathered per flow .

rollover or console cable

A rollover or console cable connects a computer or laptop to the command line terminal of a switch or router .

OSA

An optical spectrum analyzer ( OSA ) and wavelength division multiplexing ( WDM ) ensure that each channel has sufficient power .

What cable standard must POE+ use?

Cat 5e or better

ifconfig

The ifconfig command displays similar output as the ipconfig command . It can display IP information , traffic statistics , and even enable or disable a network adapter .

print route

The print route is an invalid command and will not display any results .

show mls NetFlow ip

The show mls NetFlow ip displays NetFlow IP entries .

tracert

The tracert command is used to show several details about the path that a packet takes from the computer or device whatever destination is specified .

An admin can ping the router at 192.168.105.1 from the switch . Which of the following is most likey the cause of the problem ?

Verify full system functionality and implement preventive measures

LED status indicators

indicate the status and problems with a link .

SSID

A Service Set Identifier ( SSID ) identifies a network , and the value is case - sensitive . A user will need to know the proper SSID to connect to .

VPN concentrator

A VPN concentrator is a networking device that provides the secure creation of VPN connections and the delivery of messages between VPN nodes . It is a type of router device , specifically for VPN communication infrastructures

WLAN controller

A WLAN controller manages wireless network access points that allow wireless devices to connect to the network . What a wireless access point does for a network is similar to what an amplifier does for a home stereo .

broadcast storm

A broadcast storm will cause network utilization to go to a near - maximum capacity . The CPU utilization of the switches jumps to 80 percent or more , making the switched segment effectively unusable until the broadcast storm stops

What is a cable certifier used for?

A cable certifier is used to verify that a cable meets its specifications , such as the bandwidth and frequency . For example it can verify a CAT 5e cable meets specifications and supports speeds of 1000 Mbps , and can verify a CAT 6 cable supports speeds of 10 Gbps .

What can a dirty optical cable cause?

A dirty optical cable caused by dirt , dust , or grease in the transmission path will significantly reduce signal strength block transmission entirely on fiber optic cabling .

What causes a duplicate IP address?

A duplicate IP Address occurs when another device has connected to the network and obtained the same IP address from the DHCP server .

load balancer

A load balancer is a device that acts as a reverse proxy and distributes network or application traffic across several servers . Load balancers are used to increase the capacity and reliability of applications .

What is a loop back plug?

A loopback plug is a connector used for diagnosing transmission problems on parallel and serial ports . It plugs into a port on the back of the computer .

missing route

A missing route may arise because a required static routing entry has not been entered or has been entered incorrectly Missing routes may also arise because a router fails to communicate with its neighbors and does not receive routing protocol updates .

Tone generator

A network tone generator and probe trace a cable from one end to the other by applying a signal on the cable tracing it to follow the cable over ceilings and through ducts .

packet or protocol analyzer

A packet or protocol analyzer is a software used in conjunction with a packet sniffer . It can decode a captured frame to reveal its contents in a readable format . Wireshark is a protocol analyzer .

packet sniffer

A packet sniffer will interrogate the frames received by a network adapter using a special driver ; Windows uses winpcap . It can save the captured frame into a file such as a .pcap file .

Baseline

A performance baseline establishes the resource utilization metrics at a point in time , such as when the system was first installed . This provides a comparison to measure system responsiveness later .

What is a punch down tool used for?

A punch down tool is used to assist in inserting wires into patch panels or punch down blocks .

punchdown tool

A punchdown tool has replaceable blades and fixes conductors into an IDC . Different IDC formats require different blades on the punchdown tool .

What are routing protocols used for?

A routed protocol is used to deliver application traffic . It provides appropriate addressing information in its network layer to allow a packet to be forwarded from one network to another .

How is a routing loop formed?

A routing loop is formed when an error occurs in the operation of the routing algorithm , and in a group of nodes , the path to a particular destination forms a loop .

routing loop

A routing loop occurs when two routers use one another as the path to a network . Packets are caught in a routing loop circle around until the TTL expires .

How does a short form?

A short happens when two conductors join , usually because the insulating wire is damaged or a poorly wired connector .

site survey

A site survey is performed first by examining the blueprints or floor plan of the premises to understand the layout and to identify features that might produce radio frequency interference ( RFI ) .

TAP

A test access point ( TAP ) reads the signals from the network stack and will either output two streams to monitor a full duplex link or rebuild the streams into a single channel .

What is a toner probe used for?

A toner probe is used to trace wires or cables by sending a signal from one end of a wire along its entire length

top - to - bottom approach

A top - to - bottom approach of the OSI model is a methodical validation of network components starting from the top and going down. System are at default, so basic network connectivity should be available.

What does a transceiver do?

A transceiver converts from one media type to another , uses an appropriate Ethernet standard and wavelength , and must match in pairs .

ATM

ATM's physical layer corresponds to both the physical and data link layer . The physical layer deals with the physical transmission of the bitstream and depends on the physical medium used . Copper cable or fiber optics can be used for ATMS .

Absorption

Absorption refers to the degree to which walls and windows will reduce signal strength ( some of the radio wave's energy is lost as heat when passing through construction materials ) .

What is port 20 used for?

An FTP server will listen for client connections on port 20. FTP clients will then connect to the FTP server to initiate a conversation .

external DNS server

An external DNS server is meant to offload name resolution processes to a server available on the Internet . These are mostly managed by third - party vendors

incorrect pin out

An incorrect pin - out , incorrect termination , or mismatched standards is when an installer deliberately or accidentally incorrectly wires the conductors into the terminals at one or both ends of the cable .

OTDR

An optical time - domain reflectometer ( OTDR ) locates breaks in fiber by sending light pulses down the cable and timing how long it takes for any reflections to bounce back from the break .

Which command in MS Windows displays a table consisting of IP addresses and their resolved physical addresses ?

Arp -a

Attenuation

Attenuation is the loss of signal strength that occurs as the signal travels through the media . Some media is more prone to attenuation than others .

Channel overlap

Channel overlap refers to interference issues resulting from multiple access points that are all in range of one another and are configured to use similar wavelengths .

What kind of issues can a wire map tester detect?

Continuity, short, and incorrect pin outs

Which of the following troubleshooting steps includes open and closed approaches to obtaining information ?

Questioning users is a good first step to help identify a problem . Two types of questions can be asked . Open ended questions invite a descriptive response whereas closed ended question result in a yes or no response

SMTP

SMTP , being an application layer protocol , can run on any underlying protocols , be it TCP / IP , IPX / SPX , UDP , or even on FCP .

Scope options

Scope options are a feature of the DHCP service . These options include additional settings such as default gateway and DNS server addresses .

What are risks of a BYOD program?

Security and compatibility/support

How can you solve a duplexing issue?

Setting both a NIC and switch port to auto - negotiate will solve a duplex mismatch which will slow the link down by causing high packet loss and late collisions .

When is shielded cables required?

Shielded cable is a requirement for some Ethernet standards . It may also be a requirement in environments with high interference levels as it is less susceptible to interference and crosstalk .

What is the best cabling solution to support POE?

Shielded cabling and cat 3 cable or better

Switching loops

Switching loops cause broadcast and unknown unicast frames to circulate the network perpetually , as each switch repeatedly floods each frame .

Which of the following ports would a technician need to open on a firewall to allow SSH on the default port ?

TCP port 22 is used for SSH . Secure Shell ( SSH ) is a cryptographic network protocol for operating network services securely over an unsecured network .

What is port 23 used for?

Telnet provides access to a command - line remote access to a variety of communications systems . Telnet is often used for remote maintenance of network interface on a remote computer using TCP port 23. Telnet commonly provides communications devices .

The FORWARD chain

The FORWARD chain is a firewall ruleset for connections that are passing through the server .

What port does the FTP protocol use?

The FTP protocol typically uses port 21 as its main means of communication . An FTP server will listen for client connections . FTP clients will then connect to the FTP server to initiate a conversation .

The INPUT chain

The INPUT chain is a firewall ruleset for incoming connections . Other hosts are able to ping the Linux server , so this chain does not have any issues .

Nmap

The Nmap Security Scanner is widely used for scanning remote hosts and networks , both as an auditing and a penetration testing tool .

OUTPUT chain

The OUTPUT chain is a firewall ruleset for outgoing connections . Verify that this chain does not prevent the outgoing connection using ping or the remote host's IP ( Internet Protocol ) address or name .

The PREROUTING chain

The PREROUTING chain handled packets that have just arrived , and determines via priority how to handle the packets depending on whether it is used for local processing or forwarding . This chain is processed before OUTPUT , INPUT , or FORWARD chains .

Received Signal Strength Indicator ( RSSI )

The Received Signal Strength Indicator ( RSSI ) is the strength of the signal from the transmitter at the client end .

Cisco router

The ability to use a router as a TFTP server can be quite useful . The Cisco router is the best device to use to be configured as a TFTP server .

In the OSI model, physical addressing takes place at which layer?

The data link layer ( DLL ) is responsible for the node - to - node delivery of the message . When a packet arrives in a network , it is the responsibility of DLL to transmit it to the host using its MAC address .

An administrator has just finished installing a new switch and connected two servers with IPS of 192.168.105.20 and .30 . The servers can communicate with each other but are unable to reach the Internet . What information does the admin see in the switch configuration ?

The default gateway is the path used to pass information when the device does not know where the destination is . It is a router that connects the host to remote network segments .

When trouble shooting network issues what is the first step?

The first step in the network troubleshooting methodology is to identify the problem . This can be done by gathering information and duplicating the problem .

When trouble shooting network issues, what is the fourth step to resolving it?

The fourth step in the network troubleshooting methodology is to establish a plan of action to resolve the issue .

ipconfig

The ipconfig command is only supported on Windows systems . It is used to display and verify the IP configuration .

iptables

The iptables command line utility is used to edit the rules enforced by the Linux kernel firewall . It can change INPUT , OUTPUT and FORWARD chains that are firewall rulesets .

netstat

The netstat command generates displays that show network status and protocol statistics . One can display the status of TCP and UDP endpoints in a table format , routing table information , and interface information .

nslookup

The nslookup command is a Windows utility that is used to troubleshoot domain name system ( DNS ) records . The command returns host ( A ) records by default and the set type argument is used to specify a record type . A mail exchanger ( MX ) record specifies an email server . An incorrect or missing MX record will cause mail delivery problems .

pathping

The pathping utility performs a trace route , then pings each hop router a given number of times for a given period to determine the Round Trip Time ( RTT ) for the path .

What is the physical layer responsible for?

The physical layer is responsible for the actual physical connection between the devices . The physical layer contains information in the form of bits .

What is the ping command used for?

The ping utility can be used to send a configurable number and size of ICMP ( Internet Control Message Protocol ) packets to a destination host to perform a basic connectivity test .

Effective Isotropic Radiated Power ( EIRP )

The power at which an access point transmits is configurable . Effective Isotropic Radiated Power ( EIRP ) is calculated as the sum of transmit power , antenna cable / connector loss , and antenna gain .

When trouble shooting network issues, what is the second step to reaolving it?

The second step in the network troubleshooting methodology is to establish a theory of probable cause . One may question the obvious and consider multiple approaches .

What is the session layer responsible for?

The session layer is responsible for establishing the connection , maintaining sessions , authentication , and ensuring security .

What command visualizes the general NetFlow data on the command line?

The show ip cache flow command displays the NetFlow accounting statistics . This would show a visualization of general NetFlow data .

tcpdump

The tcpdump command - line utility is a common packet analyzer that is used to display the contents of the .pcap file .

When trouble shooting network issues, what is the third to resolving it?

The third step in the network troubleshooting methodology is to test the theory to determine cause . If the theory cannot be confirmed , establish a new theory or escalate .

Throughput

Throughput is an average data transfer rate achieved over time , excluding encoding schemes , errors , and other losses incurred at the physical and data link layers .

What command line command is used to display the contents of a routing table?

To display the local routing table in MS Windows , one would open a command prompt , type route print , then press Enter . The admin can then observe the active routes by destination , network mask , gateway , interface , and metric

Show ip flow export

To display the status and the statistics for NetFlow accounting data export , including the main cache and all other enabled caches , use the show ip flow - export command in user EXEC or privileged EXEC mode . This shows more advanced accounting statistics than the show ip cache flow command .

The 802.11n wireless network is experiencing a significant amount of latency . The IPERF utility determines that the wireless network is experiencing a significant number of packets arriving out of order , arriving late , and being completely lost . What should be done ?

Try using a different channel on the WAP to reduce interference from other 2.4 GHz devices

Tenants access multiple wireless networks in a building . Users report intermittent connectivity . Which of the following is the most likely cause of the problem ?

Typically when there are multiple wireless networks within close range , there could be overlapping , which could cause intermittent connectivity issues .

Unshielded twisted pair cable

Unshielded twisted pair cable is a media type that uses copper conductors arranged in pairs that come twisted to reduce interference . Typically , cables are 4 - pair or 2 - pair .

A manager has reported a network outage at a remote branch office . After gathering some information and asking the manager and local IT personnel about the issue , a theory of probable cause cannot be established . Consider and determine what else the network support personnel can do to eventually resolve the issue ?

Verify LED status indicators and look at system logs

What is verifying full system functionality used for?

Verifying full system functionality is useful to identify the results and effects of a solution . Having a user try to recreate the issue after a fix is a good test .

What does a loopback adapter test for?

a network loopback adapter sends the packet back to itself to test for bad ports and network cards .

cable crimper

cable crimper creates a patch cord and fixes a plug to a cable . The tools are specific to the type of connector and cable .

bottom - to - top approach

components starting from the bottom or layer 1 ( Physical ) and going up . This is most appropriate because cables have A bottom - to - top approach of the OSI ( Open System Interconnection ) model is a methodical validation of network just been connected .

light meter

fiber light meter , which may come together with an optical source as a fiber testing kit , can be used to detect attenuation on fiber optic cable .

cable stripper

installers can use a cable stripper when working with multiple cable types as cable strippers have replaceable blades for different data cable types .

fusion splicer

joins two fiber optic cables together by performing a precise alignment between the two strands and then permanently joining them using an arc weld .

cable tester

reports detailed information on the cable's physical and electrical properties , including crosstalk , attenuation , noise , and resistance .

multimeter

test electrical circuits , but it can test for the continuity of any copper wire if a cable tester is not available .

Iperf

Iperf is a network performance utility that can generate TCP and UDP traffic to test bandwidth , latency , and packet loss .

What would a technician find in a network map?

MDF/IDF's

Refection

Mirrors or shiny surfaces cause signals to reflect , meaning that a variable delay is introduced . Refection causes packets to be lost and consequently the data rate to drop .

Nmap

Nmap is a highly adaptable , open - source network scanner used primarily to scan hosts and ports to locate services and detect vulnerabilities .

Noise

Noise is anything transmitted within or close to the channel that is not the intended signal , causing errors in data and forcing retransmissions . This is known as the signal - to - noise ratio ( SNR ) .

A technician tries the suggested troubleshooting steps to remedy a computer issue . The steps do not fix the problem . Additional suggestions are at a support website that discuss a different cause and potential fix for the problem . What troubleshooting path should the technician follow ?

Often problems may have several different possible causes . When a theory is not confirmed , the next in line can be considered . Escalation means referring the problem to a more knowledgeable entity such as a senior technician , manager , or third party .

Polarization

Orientation of the wave propagating from the antenna to maximize signal strength ; the transmission and reception antennas should normally use the same polarization

A wireless access point ( WAP ) resides in the middle of an office area . A network administrator wants to gather information about data packets coming through the WAP for subsequent examination . Which of the following will provide the minimum level of support for completion of this task ?

Packet sniffer

Ping

Ping is the primary TCP / IP command used to troubleshoot connectivity , reachability , and name resolution . This command can be used to test both the computer name and the IP address of the computer .

PoE

Power over Ethernet ( PoE ) supplies electrical power from a switch port over standard data cabling to a connected powered device ( PD ) .

Telnet protocol is used to establish a connection to which port?

Port 23

Ipconfig / all

Ipconfig / all displays all configuration information for each adapter bound to TCP / IP .

A network engineer troubleshoots an issue where clients are not receiving IP addresses from a new , properly configured DHCP server on another subnet . Statically addressed clients can get onto the same network with no issues . Which of the following is causing the issue ?

DHCP IP Helper addresses are configured on a routed interface that allows that specific device to act as a " middle man , " which forwards Broadcast DHCP to the DHCP server .

A user took a laptop on vacation and made changes to the configuration in order to use the device at the hotel . The user can reach the Internet , but cannot access any internal network resources . Which of the following is the most likely reason ?

DNS servers translate domain names into IP addresses , making it possible for DNS clients to reach the origin server . It is the phonebook of the Internet , connecting web browsers with websites . Having an incorrect DNS would cause issues connecting to internal resources as described .

Decibels

Decibels ( dB ) express attenuation or the loss of signal strength . dB expresses the ratio between two measurements : signal strength at origin and signal strength at the destination .

A new stack of servers and other devices have recently been installed in the communications closet . After powering on the devices , there were obvious network issues when the admin looked at the back of the devices . Justify why the network admin should use a bottom - to - top approach to troubleshoot the issue .

Devices that were recently cabled to the network and installed in the communications room would justify a review of physical cables and ports ,

Dig

Dig can identify IP address records , record the query route to obtain answers from an authoritative nameserver , and diagnose other DNS problems

A user calls to report that email is not working and that there is a printer jam. Which troubleshooting approach is best?

Discovering symptoms of more than one problem is common . When problems do not seem to be related , it is best to treat each issue as a separate case .

Electrician's scissors , or snips

Electrician's scissors , or snips , cut copper wire and stripping insulation and cable jackets . Manufacturers make cable cutting blades rounded to preserve the wire geometry .

Why might APIPA addresses be assigned?

Exhausted DHCP scope

FTP

FTP is an application layer protocol and can run on any underlying protocols , such as TCP / IP , IPX / SPX , UDP , or even on FCP .

Flow exporters

Flow exporters are created as separate components in a router's configuration . Exporters are assigned to flow monitors to export the data from the flow monitor cache to a remote system .

What NetFlow component can be applied to an interface to track IPv4 traffic?

Flow monitor

Flow samplers

Flow samplers are created as separate components in a router's configuration . Flow samplers are used to reduce the load on the device by limiting the number of packets that are selected for analysis .

refraction

Glass or water can cause radio waves to bend and take a different path to a receiver and cause the data rate to drop . This is known as refraction .

HTTP ,

HTTP , being an application layer protocol , can run on any underlying protocols , be it TCP / IP , IPX / SPX , UDP , or even on FCP .

IPAM

IPAM or Internet Protocol ( IP ) address management is designed to scan Dynamic Host Configuration Protocol ( DHCP and Domain Name System ( DNS ) servers and log IP address usage to a database . It can be used to manage and reconfigure DHCP and DNS servers remotely .

What does a wrong default gateway cause?

If the PC is configured with an incorrect default gateway , the PC will attempt to forward to what is configured and arp for the address that is configured

An administrator purposely created a cable with an incorrect pin - out so that the cable could connect two hosts together for direct communication . What kind of cable did the administrator create ?

In a crossed pair cable ( TX / RX reverse ) , the conductors from one pair are connected to pins belonging to a different pair and could be done deliberately to create a crossover cable to link two hosts but would not link a host to a switch .

What is a divide and conquer approach?

In a divide and conquer approach , rather than starting at the top or bottom of the OSI reference model , a start is initiated with the layer most likely to be causing the problem .

What does mismatched SSIDs cause?

Incorrect encryption settings and mismatched SSIDs would not result in latency but would result in the client system not being able to connect at all .

What can interference cause?

Interference can cause issues with throughput and can come from sources such as electrical power cables , fluorescent lights , motors , electrical fans , radio transmitters .