Module 12: Network Troubleshooting Flashcards
What are the four common types of network documentation?
- Physical topology
- Logical topology
- Network device documentation
- Network performance baseline documentation
What information is typically included in a physical topology diagram?
- Device name
- Device location (address, room number, rack location, etc.)
- Interface and ports used
- Cable type
What information might be documented for a router in network device documentation?
- Interface
- IPv4 address
- IPv6 address
- MAC address
- Routing protocol
What information might be documented for a switch in network device documentation?
- Ports enabled
- Access
- VLAN
- Trunk
- Link Aggregation (EtherChannel/LACP)
- Native VLAN
- Enabled status
What information might be documented for end-systems in network device documentation?
- Device name
- Operating system
- Services
- MAC address
- Static IPv4 and IPv6 addresses
- Default gateway
- DNS servers
What key questions should a network baseline answer?
- How does the network perform during a normal day?
- Where are the most errors occurring?
- What part of the network is most heavily used?
- What part of the network is least used?
- Which devices should be monitored, and what alert thresholds should be set?
- Can the network meet the identified policies?
What factors should be considered when conducting an initial network baseline?
Select key variables such as interface and CPU utilisation, and collect data for a long enough period to determine a “normal” network behaviour.
How can a logical network topology diagram assist with network monitoring?
It helps identify key devices and ports that should be monitored for performance and security
What commands can be used to gather information directly from routers and switches?
show, ping, traceroute, telnet/SSH and CDP/LLDP commands
What are the seven steps of the troubleshooting process?
- Define the problem
- Gather information
- Analyze information
- Eliminate possible causes
- Propose a hypothesis
- Test the hypothesis
- Solve the problem
What types of questions should be asked when gathering information from end users about network problems?
Both open-ended and closed-ended questions.
What commands can be used to gather information from network devices?
show, ping, traceroute, and telnet
What troubleshooting approaches use the OSI or TCP/IP layered models?
Bottom-up, top-down, and divide-and-conquer troubleshooting.
What are other troubleshooting methods besides the layered approach?
Follow-the-path, substitution, comparison, and educated guess.
Which troubleshooting approach is commonly used for software-related problems?
Top-down troubleshooting.
Which troubleshooting approach is commonly used for hardware-related problems?
Bottom-up troubleshooting.
What troubleshooting approach is often used by experienced technicians for new or unknown problems?
Divide-and-conquer troubleshooting.
What are common software troubleshooting tools?
NMS tools, knowledge bases, and baselining tools.
What is the function of a protocol analyzer such as Wireshark?
It decodes the various protocol layers in a recorded frame and presents the information in an easy-to-use format.
What are common hardware troubleshooting tools?
Digital multimeters, cable testers, cable analyzers, portable network analyzers, and Cisco Prime NAM.
How can a syslog server be used for troubleshooting?
It collects and stores event messages from network devices, allowing administrators to track configuration changes, ACL violations, interface status, and other critical events.
Where can Cisco devices send log messages?
Console, terminal lines, buffered logging, SNMP traps, and syslog servers.
How does syslog severity level numbering work?
The lower the level number, the higher the severity of the message.
What does the logging trap level command do?
It limits messages logged to the syslog server based on severity, only logging messages equal to or numerically lower than the specified level.
