Following are the stages for gathering symptoms for a network problem:
Stage 1 – Analyze Existing Symptoms
The troubleshooter analyzes
symptoms gathered from the trouble ticket, users, or end systems affected by
the problem to form a definition of the problem.
Stage 2 – Determine
Ownership
If the problem is in the troubleshooter’s system, it will be
necessary to move on to stage 3. If the problem is outside the boundary of the
troubleshooter’s control, it will be necessary to contact an administrator for
the external system before gathering additional network symptoms.
Stage 3 – Narrow Scope
The troubleshooter determines if the
problem is at the core, distribution or access layer of the network. At the
identified layer use an analysis of existing symptoms and knowledge of the
network topology to determine which piece or pieces of equipment are the most
likely cause.
Stage 4 – Determine Symptoms
Using a layered
troubleshooting approach, the troubleshooter gathers hardware and software
symptoms from the suspect devices. The technician starts with the most likely
possibility and uses knowledge and experience to determine if the problem is
more likely a hardware or software configuration problem.
Stage 5 –
Document Symptoms
Document any hardware or software symptoms. If the
problem can be solved using the documented symptoms, a troubleshooter will
solve the problem and document the solution. If the problem cannot be solved,
the technician begins the isolating phase of the general troubleshooting
process.

Be
prudent with use of the debug command on a network. It generates enough console
message traffic that the performance of a network device can be noticeably
affected. Be sure to disable debugging when its capabilities are no longer
needed.