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Chapter 11

Chapter 11. Troubleshooting. Introduction. Bottom up. Top Down. General Problem Solving Model. Is there an accurate physical and logical map of the network? Does it have a logical map of network addresses, network numbers, subnetworks, and so forth?

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Chapter 11

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  1. Chapter 11 Troubleshooting

  2. Introduction Bottom up Top Down

  3. General Problem Solving Model

  4. Is there an accurate physical and logical map of the network? Does it have a logical map of network addresses, network numbers, subnetworks, and so forth? Is there an established baseline for the network? Has the organization documented normal network behavior and performance at different times of the day? Is there a list of all network protocols implemented in the network? For each of the protocols implemented, is there a list of the network numbers, subnetworks, zones, areas, and so on that are associated with them? Which protocols are being bridged? What are the points of contact to external networks, including any connections to the Internet? For each external network connection, what routing protocol is being used ? Preparation

  5. Performance Management – measure network performance (throughput, response times, and utilitzation) and provide tools to maintain it at an acceptable level. • Configuration Management – Monitor operations to manage hardware and software configurations. • Accounting Management – Regulate individual or group use so network resources can be distributed based on resource capabilities. • Fault Management – detect, log, notify users of, and fix network problems. • Security Management – control access to network resources according to local guidelines.

  6. OSI Troubleshooting

  7. Wireless Sniffers

  8. Interference • A spectrum analyzer is the best tool to determine if there is activity on a frequency • Interference and signal degradation sources include the following: • Radio Interference – unlicensed spectrum  • Electromagnetic Interference –. EMI is more likely to affect the components of the transmitter rather than the transmission. • Cordless Phones or other 2.4-GHz wireless devices – • Change the location of the AP or the base of the cordless phone. • Try switching to channel 1 or channel 11 on the AP. • Use a remote antenna on the client card if that is an option. • Operate the phone with the antenna lowered, if possible. • Use a 900-MHz phone instead of a 2.4-GHz phone.

  9. EMFs • Gauss and tesla meters   A gauss meter measures electric and magnetic fields (EMFs), which are produced by power lines, electrical wiring, and electrical equipment. • EMFs are invisible lines of force that surround any electrical device. Electric fields are produced by voltage and increase in strength as the voltage increases. • Electric fields are present even when the equipment is switched off, as long as it remains connected to the source of electric power. • Electric fields are shielded or weakened by materials that conduct electricity including trees, buildings, and human skin. Magnetic fields pass through most materials and are therefore more difficult to shield. Both electric and magnetic fields decrease as the distance from the source increases.

  10. Firmware Upgrades

  11. Client Adapter Status LEDs RF traffic LEDs

  12. Antenna Cable -Loose connections. -Damaged cables -Cable runs shared with power cables creating EMIs -Water in cable connections -

  13. Obstacles • When connecting two points, the distance between them, obstructions, and antenna location must all be considered.

  14. Line of Sight to consider Fresnel zone Appropriate Antenna – omnidirectional or directions Antenna placement and support structure in various weather conditions Proper antenna alignment and testing Glass – if signal is passing through glass, metallic tinting on the glass can degrade the signal. Weather – high winds, rain, fog etc will degrade the signal Obstacles

  15. System Logging • The administrator can use the information in a log to tell whether the AP or bridge is working properly or whether it has been compromised. Logging can be achieved via local logging, syslog, or SNMP. • The logs should be sent to a designated log host. When the logging process is disabled, messages are sent only to the console real time. • Logs must be reviewed regularly • Accurate timestamps are important to logging. • The severity level of the messages can be set to control the type of messages displayed on the console and each of the destinations.

  16. System Error Levels

  17. SNMP • Managed devices • Agents – software that resides on managed devices • Network-management system (NMS) - An NMS executes applications that monitor and control managed devices • MIB – database that resides on the managed device • Trap – event notification send from the agent to the NMS • Community – string value that provides a simple password

  18. Enterprise Management • Cisco WLAN Solution Engine (WLSE) - CiscoWorks WLSE provides centralized, turnkey management for the Cisco Wireless LAN infrastructure. • Cisco Aironet Configuration Administration Tool (ACAT) - a tool used by administrators to specify software installation options for client adapters located in PCs running a Windows operating system • Wavelink is a developer of wireless solutions to deploy and manage enterprise wireless applications and infrastructure. • The AirWave Management Platform is a network management solution specifically designed for a multi vendor wireless networks

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