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 .