Troubleshooting guide

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Cisco Broadband Local Integrated Services Solution Troubleshooting Guide
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Chapter 2 Troubleshooting Overview
Troubleshooting Tools
Network Management Systems
As networks grow larger and more complex, there is a greater chance of network failures that can disable
the entire network or degrade performance to an unacceptable level. The complexity of such large
networks makes the use of automated network management tools a critical factor in efficient
management. It is important that the continued addition of users, interfaces, protocols, and vendor
equipment to the network does not result in the network manager losing control of these resources and
how they are used. It is also important that as network resources become more critical in an
organization's operations, downtime be reduced. To ensure maximum network availability, network
managers should include network management in their internetwork designs.
The International Organization for Standardization (ISO) has defined five key functional areas of
network management: fault management, configuration management, accounting management,
performance management, and security management, commonly called FCAPS.
The functions of fault, performance, and configuration management are most applicable to a
troubleshooting environment. To achieve maximum network availability, all individual components of a
network must be maintained in working order. A key ingredient to achieving this is having a mechanism
in place that reports a fault immediately as it occurs. A fault can be defined as an abnormal network
event, usually indicated by network components failing to operate correctly or causing excessive errors.
It is therefore important to be able to do the following:
• Determine exactly where the fault has occurred.
• Isolate the failed area from the rest of the network so that the rest of the network can continue
operating.
• Reconfigure or modify the network or its configuration to minimize the impact of operating without
the failed component or affected portions of the network.
• Repair or replace the failed components to restore normal network operation.
Configuration management involves several functions. The network manager should be able to set up the
network by initial configuration of the network components and interactively control these components
by changing their configuration in response to performance evaluation or in response to network
upgrades or fault recovery.
SNMP is an application-layer protocol that facilitates the exchange of management information between
network devices. It is part of the TCP/IP protocol suite. SNMP enables network administrators to
manage network performance, find and solve network problems, and plan for network growth. An SNMP
network consists of SNMP agents (managed devices) and an SNMP management station (manager).
In a typical SNMP design an SNMP manager queries an SNMP agent on a router to obtain operational
statistics from the agent.
Simulation and Modeling Tools
Simulation/modeling software is useful for purposes such as initial network design, analysis of a
network reconfiguration or redesign, and stress-testing a network.
This type of software usually uses object-oriented design to predict the performance of networks,
ranging from departmental LANs up to complex, enterprisewide internetworks and WANs.
By selecting numerous objects that represent network topology, protocols in use, traffic, and routing
algorithms, Netsys Baseliner attempts to simulate the operation of the network. Most types of LAN,
MAN, and WAN technologies can be modeled by these tools. The output gives measures of the network
performance such as response times; network throughput; node, link, and LAN utilization; packets
dropped; and other performance data.