Chapter 12- Network Troubleshooting

Top-down troubleshooting

-Starts at the application layer and works down the OSI Layers to the Physical Layer -suitable for simpler problems that are suspected to be application/user or upper-layer related -If the problem turns out to be related to lower layers you have wasted a lot of time and effort at the upper layers

Bottom-up troubleshooting

-Starts at the physical layer and works up the OSI model -More suited for complex cases -slow but solid approach -If the problem turns out to be related to the application layer then a lot of time and effort was wasted at the lower levels

Substitution troubleshooting

-also called swap the component

Spot-the-differences troubleshooting (comparison)

-changes the nonoperational elements to be consistent with the working ones.

Follow-the-path Troubleshooting

-objective is to eliminate the links and devices that are irrelevant to the troubleshooting task at hand.

Divide-and-conquer troubleshooting

-typically begins with one of the middle layers and moves either up or down -Most suitable when experiencing problems with precise symptoms -approaches the layer of the culprit faster but requires experience

Physical Topology

A topology that describes a network's physical layout and shape. includes the device name, device location (address, room number, rack location), interface and ports used, cable type

General Troubleshooting Procedures step 4 if problem solved:

Document solution and save changes

General Troubleshooting Procedures step 1:

Gather Symptoms

General Troubleshooting Procedures step 3:

Implement Corrective Action

General Troubleshooting Procedures step 2:

Isolate the Problem

Knowledge Bases

Online network device vendor sources of information

network baseline

answers - How does the network perform during a normal or average day? -Where are the most errors occurring? -What part of the network is most heavily used? -Which devices should be monitored and what alert thresholds should be set? -Can the network meet the identified policies?

Network Management system tools

includes device-level monitoring, configuration, and fault-management tools. These tools can be used to investigate and correct network problems.

Logical IPv4 Topology

refers to how devices transfer data across the network when communicating with other devices. Includes device ID's, IPv4 addresses, interface identifiers, Routing protocols/ Static routes, Layer 2 info (i.e., VLANS, trunks, Etherchannels). Can use IPv4 or IPv6

Logical IPv6 Topology

refers to how devices transfer data across the network when communicating with other devices. Includes device ID's, IPv6 addresses, interface identifiers, Routing protocols/ Static routes, Layer 2 info (i.e., VLANS, trunks, Etherchannels). Can use IPv4 or IPv6

baselining tools

tools for automating the network documentation and establishing a starting point

General Troubleshooting Procedures step 4 if problem not solve:

undo corrective action and start again

shoot-from-the-hip troubleshooting (Educated Guess)

usually should only be used by experienced technicians, usually too random to be effective