Network Troubleshooting

Question 1

phenomenon where an electrical signal from one wire bleeds into another wire, creating interference

Answer 1

crosstalk

Question 2

spurious signals caused by faulty hardware or badly crimped jacks

Answer 2

noise

Question 3

cable problem caused by the connection of two cables with difference impedances (natural resistance), resulting in echo

Answer 3

impedance mismatch

Question 4

tool used to see if a cable can handle the rated amount of capacity; checks for crosstalk, attenuation, interference, and even impedance mismatch; used when there is a slowdown, not disconnects; needs some kind of loopback adapter installed at the other end of the cable

Answer 4

certifier

Question 5

tool used to measure the amount of light loss in an fiber cable; a calibrated detector is installed at the other end of the cable

Answer 5

light/optical power meter

Question 6

tool used to tell if there is a power/electrical problem with a cable/device?’ used to check intermittent problems

Answer 6

voltage quality recorder

Question 7

tool used to measure the temperature in a room, like a server room; used to check intermittent problems

Answer 7

temperature monitor

Question 8

utility used to inform one of the IP information/settings for a computer; for Windows, Macos/UNIX, and Linux respectively

Answer 8

ipconfig/ifconfig/ip

Question 9

utility that resolves an IP address to a MAC address; stored on computers and Level 3 devices (routers)

Answer 9

Address Resolution Protocol (arp)

Question 10

utility that uses ARP frames instead of ICMP packets to query a device; can only be used within a broadcast domain - can’t cross routers since it doesn’t use IP packets, only frames; supported by UNIX and UNIX-like systems

Answer 10

arping

Question 11

Microsoft utility that combines the functionality of ping and tracert

Answer 11

pathping

Question 12

utilities used to troubleshoot DNS issues; supported by all OS’s and MacOS/UNIX/Linux respectively

Answer 12

nslookup/dig

Question 13

dynamic equivalent to tracert, not supported by Windows

Answer 13

My Traceroute (mtr)

Question 14

utility used to display a device’s routing table

Answer 14

route

Question 15

utility used to display the state of all running processes; shows which sessions are active and provide statistics based on ports and protocols; without switches, this command only shows current sessions

Answer 15

netstat

Question 16

Linux utility that enables control over IPv4 tables - rules that determine what happens to IPv4 packets on a firewall; replaced by nftables

Answer 16

iptables

Question 17

Linux/UNIX command line tool that monitors and filters network packets and it can create files for later viewing in Wireshark

Answer 17

tcpdump

Question 18

tool used to measure the flow of data through a network

Answer 18

throughput/bandwidth speed tester

Question 19

remote servers accessed via a web browser that provides diagnostic tools like ping and tracert from outside the local network; also provides some BGP query tools

Answer 19

looking glass site

Question 20

technology that combines multiple NICs together in order to increase bandwidth in smaller increments (and cheaper) than upgrading NICs to the next standard; can also create redundancy by setting one NIC to primary (live) and the other to hot spare (standby)

Answer 20

link aggregation/NIC teaming

Question 21

IEEE 802.3ad protocol for enabling two or more network connections to work together simultaneously; ports can be in active or passive mode and must communicate at the same speeds

Answer 21

Ling Aggregation Control Protocol (LACP)

Question 22

Cisco proprietary protocol for combining multiple network connection into one logical connection

Answer 22

Port Aggregation Protocol (PAgP)

Question 23

issue where one’s IP packets are so large that they must be fragmented to fit into an ISP’s packets

Answer 23

MTU mismatch

Question 24

method for automatically determining the right MTU size; this-aware OS can send ICMP packets with a “Don’t Fragment” flag (DF) to another device until the ping is successful; worthless if firewall is set to block ICMP requests

Answer 24

Path MTU Discovery (PMTU)

Question 25

Cisco network appliance, which possibly contains routing, NAT, switching, and IDS features, plus firewall

Answer 25

Cisco Adaptive Security Appliance (ASA)

Question 26

problem where the NAT rule order on a "router"/network appliance is incorrect, causing traffic to go out an incorrect interface

Answer 26

NAT interference misconfiguration

Question 27

process of making remote computers act as though they are on a local network, such as VPN; almost all such problems occur on the VPN concentrator, which can cause what appears to be a DoS attack

Answer 27

proxy ARP

Question 28

principle stating that work should happen only on the endpoints of a network

Answer 28

end-to-end principle