Categorize The Problem; Identify The Root Cause Of The Problem - Alcatel 5620 Troubleshooting Manual

Categorize the problem

When you categorize a problem, you must differentiate between total failures and
problems that result in a degradation in performance. For example, the failure of an
access router results in a total failure for a customer who has one DS3 link into a
network. A core router that operates at over 80% average utilization can start to
discard packets, which results in a degradation of performance for some applications
that use that router. Performance degradations exhibit different symptoms from total
failures and may not generate alarms or significant network events.
Multiple problems can simultaneously occur and create related or unique symptoms.
Detailed information about the symptoms that are associated with the problem helps
the NOC or engineering operational staff diagnose and fix the problem. The
following information can help you assess the scope of the problem:
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alarm files
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error logs
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network statistics
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network analyzer traces
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core dumps
Use the following guidelines to help you categorize the problem:
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Is the problem intermittent or static?
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Is there a pattern associated with intermittent problems?
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Is there an alarm or network event that is associated with the problem?
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Is there congestion in the routers or network links?
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Is there a change in the network delta since proper function?

Identify the root cause of the problem

A symptom for a problem can be the result of more than one network issue. You can
resolve multiple, related problems by resolving the root cause of the problem. Use
the following guidelines to help you implement a systematic approach to resolve the
root cause of the problem:
•
Identify common symptoms across different areas of the network.
•
Focus on the resolution of a specific problem.
•
Divide the problem based on network segments and try to isolate the problem to
one of the segments. Examples of network segments are:
•
Determine the network state before the problem appeared.
•
Extrapolate from network alarms and network events the cause of the symptoms.
Try to reproduce the problem.
Alcatel 5620 Service Aware Manager, Release 2.1 R2
May 2005 95-5887-01-00-B
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LAN switching (edge access)
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LAN routing (distribution, core)
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metropolitan area
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WAN (national backbone)
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partner services (extranet)
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remote access services
1 — Troubleshooting process
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serial line traces
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stack dumps
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output of CLI show commands
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accounting logs
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customer problem reports
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