Chapter 12 - Network Troubleshooting Flashcards
what structured troubleshooting method starts at the physical layer and physical components of the network?
bottom-up
what structured troubleshooting method starts with end-user applications and moves down through OSI model
Top-down
what structured troubleshooting method selects a layer based on informed guess and tests in both directions from that layer?
divide and conquer
what structured troubleshooting method discovers traffic path all the way from source to destination and eliminates links and devices not relevant to troubleshooting task?
follow-the-path
what structured troubleshooting method do you physically swap the problematic device with a known, working one?
substitution, also called swap-the-component
what structured troubleshooting method uses educated guesses based on symptoms of the problem?
Educated Guess
what structured troubleshooting method attempts to resolve problem by changing the nonoperational elements to be consistent with the working one?
Comparison
what is the highest OSI layer that should be considered when troubleshooting routers and Layer 3 switches?
Layer 4
three software troubleshooting tools
- network management system tools
- knowledge bases
- baselining tools
what types of info does a protocol analyzer display?
- physical layer bit data
- data link layer info
- protocols
- description for each frame
which hardware troubleshooting tool is used to verify that a network device is receiving power
Digital Multimeter
which hardware troubleshooting tool can detect broken wires, crossed-over wiring, shorted connections and improperly paired connections
Cable Testers
which hardware troubleshooting tool can be used to pinpoint the distance to a break in a cable
Time-domain Reflectometers.
Optical TDRs for fiber-optic cables
which hardware troubleshooting tool used to test and certify copper and fiber cables for different services and standards
Cable Analyzers
which hardware troubleshooting tool is used for troubleshooting switched networks and VLANs?
Portable Network Analyzers
Where can Cisco devices send event messages to?
- console
- terminal line
- buffered logging
- SNMP traps
- syslog
Cisco IOS msgs, what levels are considered Highest levels and what levels are considered Lowest levels?
Highest - Level 0 - 4
Lowest - Level 5 -7
Cisco IOS command to set message levels to be logged
logging trap
Which OSI layer are you troubleshooting when investigating an extended ACL related problem
Transport
Which OSI layer are you troubleshooting when investigating a DNS related problem
Application
Which IOS command can be used to test if other network protocols are working
Telnet
what are some common symptoms of physical layer network problems?
- performance lower than baseline
- loss of connectivity
- network bottlenecks or congestion
- high CPU utilization rates
- console error messages
what are some common causes of physical layer problems?
- power-related (fundamental reason for network failure)
- hardware faults (NICs)
- cabling faults
- attenuation
- noise
- interface config error
- exceeding design limit
- CPU overload
symptoms of data link layer network problems
- no functionality or connectivity at network layer or above
- network operating below baseline performance levels
- excessive broadcasts
- console messages
causes of data link layer network problems
- encapsulation errors
- address mapping errors
- framing errors
- STP failure or loops
symptoms of network layer problems
- network failure
- suboptimal performance
no single template for solving Layer 3 problems. What are the areas to explore when diagnosing problem involving routing protocols for network layer troubleshooting?
- general network issues
- connectivity issues
- routing table
- neighbor issues
- topology database
transport layer troubleshooting - common improper config of ACLs
- selection of traffic flow
- order of ACL entries (specific to general)
- implicit deny any
- address and IPv4 wildcard mask
- selection of transport layer protocol
- src and dst ports
- use of the established keyword
- uncommon protocols (VPN and encryption protocol)
transport layer troubleshooting - common interoperability areas when having issues with NAT
- BOOTP and DHCP - difficulty operating over a router running static or dynamic NAT
- DNS
- SNMP
- Tunneling and encryption protocols
what are the application protocols to consider when troubleshooting application layer
- ssh/telnet
- http
- ftp
- tftp
- smpt
- pop
- snmp
- dns
- nfs
