Internetworking Troubleshooting Handbook

Internetworking Troubleshooting Handbook

by Cisco Systems Inc, Kevin Downes
Cisco's TAC team<197>the elite of troubleshooting professionals<197>have reviewed and revised the first edition of Internetwork Troubleshooting Handbook to ensure that today's internetworking professionals will be able to solve everyday problems in their networks. This book provides the information necessary to troubleshoot many problems commonly encountered in


Cisco's TAC team<197>the elite of troubleshooting professionals<197>have reviewed and revised the first edition of Internetwork Troubleshooting Handbook to ensure that today's internetworking professionals will be able to solve everyday problems in their networks. This book provides the information necessary to troubleshoot many problems commonly encountered in internetworks using Cisco hardware and software products, enabling readers to diagnose and resolve specific problems common to every network type. It will help readers reduce downtime, improve network performance, and enhance network reliability using proven troubleshooting solutions. Readers will be able to make intelligent, timely, and cost-effective networking decisions for their networking environments. Each section of the book is devoted to problems common to a specific protocol or topology. Sections are subdivided into symptoms, descriptions of environments, diagnosing and isolating problem causes, and problem-solution summaries.

Editorial Reviews
The Barnes & Noble Review
Wouldn't it be great if you could benefit from the shared troubleshooting expertise of Cisco's Technical Assistance Center professionals -- without paying for a support contract?

You can, with Internetworking Troubleshooting Handbook, Second Edition. In this book, Cisco's TAC engineers bring together the most valuable solutions and techniques they've learned for troubleshooting problems in nearly any element of an enterprise network, regardless of protocol or technology.

The book starts with a general "problem-solving model" for network troubleshooters and a quick look at the tools of the troubleshooting trade. Then, it's on to hardware. Why won't that Cisco 7000 router boot? (Or that Catalyst 5000 switch?) How do you identify Ethernet media problems from the IOS command line?

You'll find chapter-length coverage on troubleshooting several key desktop and enterprise routing protocols, including, of course, TCP/IP and IPX, but also IBM, AppleTalk, DECnet, and others. There are step-by-step instructions for tracking down problems in serial lines and dial-up connections; ISDN; and especially in Frame Relay networks (what to do when the link is down, when you can't ping a remote router, or when you can't ping end-to-end).

From LAN switching to transparent bridging, ATM PVCs to security, you'll find specific guidance (including what to do before you call TAC). There's even a chapter on troubleshooting CiscoWorks 2000 network management systems.

Bottom line: With this book's 1,000-plus pages of solutions, you can get your Cisco network back to good health faster. What more could you ask? (Bill Camarda)

Bill Camarda is a consultant and writer with nearly 20 years' experience in helping technology companies deploy and market advanced software, computing, and networking products and services. His 15 books include Special Edition Using Word 2000 and Upgrading & Fixing Networks For Dummies®, Second Edition.

Product Details

Pearson Education
Publication date:
Networking Technology Series
Product dimensions:
7.83(w) x 9.43(h) x 2.57(d)

Read an Excerpt

2. Troubleshooting Toools


CiscoView graphical management features provide dynamic status, statistics, and comprehensive configuration information for Cisco internetworking products (switches, routers, hubs, concentrators, and access servers). CiscoView aids network management by displaying a physical view of Cisco devices and color-coding device ports for at-a-glance port status, allowing users to quickly grasp essential information. Features include the following:

  • Graphical displays of Cisco products from a central location, giving network managers a complete view of Cisco products without physically checking each device at remote sites
  • A continuously updated physical view of routers, hubs, switches, or access servers in a network, regardless of physical location
  • Updated real-time monitoring and tracking of key information and data relating to device performance, traffic, and usage, with metrics such as utilization percentage, frames transmitted and received, errors, and a variety of other device-specific indicators
  • The capability to modify configurations such as trap, IP route, virtual LAN (VLAN), and bridge configurations

    Internetwork Performance Monitor

    IPM is a network management application that enables you to monitor the performance of multiprotocol networks. IPM measures the response time and availability of IP networks on a hop-by-hop (router-to-router) basis. It also measures response time between routers and the mainframe in Systems Network Architecture (SNA) networks.

    Use IPM to perform the following tasks:

  • Troubleshoot problems by checking the network latency between devices
  • SendSimple Network Management Protocol (SNMP) traps and SNA alerts when a user-configured threshold is exceeded, when a connection is lost and re-established, or when a timeout occurs
  • Analyze potential problems before they occur by accumulating statistics, which are used to model and predict future network topologies
  • Monitor response time between two network end points

    The IPM product is composed of three parts: the IPM server, the IPM client application, and the response time reporter (RTR) feature of the Cisco IOS software.

    The TrafficDirector RMON Application

    The TrafficDirector advanced packet filters let users monitor all seven layers of network traffic. Using Cisco IOS embedded RMON agents and SwitchProbe standalone probes, managers can view enterprise-wide network traffic from the link, network, transport, or application layers. The TrafficDirector multilayer traffic summary provides a quick, highlevel assessment of network loading and protocol distributions. Network managers then "zoom in" on a specific segment, ring, switch port, or trunk link and apply real-time analysis and diagnostic tools to view hosts, conversations, and packet captures.

    TrafficDirector threshold monitoring enables users to implement a proactive management environment. First, thresholds for critical Management Information Base (MIB) variables are set within the RMON agent. When these thresholds are exceeded, traps are sent to the appropriate management station to notify the network administrator of an impending problem.

    The VIanDirector Switch Management Application

    The VLanDirector switch management application simplifies VLAN port assignment and offers other management capabilities for VLANs. VlanDirector offers the following features for network administrators:

  • Accurate representation of the physical network for VLAN design and configuration verification
  • Capability to obtain VLAN configuration information on a specific device or link interface
  • Discrepancy reports on conflicting configurations
  • Capability to troubleshoot and identify individual device configurations that are in error with system-level VLANs
  • Quick detection of changes in VLAN status of switch ports
  • User authentication and write protection security

    Third-Party Troubleshooting Tools

    In many situations, third-party diagnostic tools can be more useful than commands that are integrated into the router. For example, enabling a processor-intensive debug command can be disastrous in an environment experiencing excessively high traffic levels. However, attaching a network analyzer to the suspect network is less intrusive and is more likely to yield useful information without interrupting the operation of the router. The following are some typical third-party troubleshooting tools used for troubleshooting internetworks:

  • Volt-ohm meters, digital multimeters, and cable testers are useful in testing the physical connectivity of your cable plant.
  • Time domain reflectors (TDRs) and optical time domain reflectors (OTDRs) are devices that assist in the location of cable breaks, impedance mismatches, and other physical cable plant problems.
  • Breakout boxes, fox boxes, and BERTs/BLERTs are useful for troubleshooting problems in peripheral interfaces.
  • Network monitors provide an accurate picture of network activity over a period of time by continuously tracking packets crossing a network.
  • Network analyzers such as sniffers decode problems at all seven OSI layers and can be identified automatically in real time, providing a clear view of network activity and categorizing problems by criticality.

    Volt-Ohm Meters, Digital Multimeters, and Cable Testers

    Volt-ohm meters and digital multimeters are at the lower end of the spectrum of cabletesting tools. These devices measure parameters such as AC and DC voltage, current, resistance, capacitance, and cable continuity. They are used to check physical connectivity.

    Cable testers (scanners) also enable you to check physical connectivity. Cable testers are available for shielded twisted-pair (STP), unshielded twisted-pair (UTP), I0BaseT, and coaxial and twinax cables. A given cable tester might be capable of performing any of the following functions:

  • Test and report on cable conditions, including near-end crosstalk (NEXT), attenuation, and noise
  • Perform TDR, traffic monitoring, and wire map functions
  • Display Media Access Control (MAC)-layer information about LAN traffic, provide statistics such as network utilization and packet error rates, and perform limited protocol testing (for example, TCP/IP tests such as ping)

    Similar testing equipment is available for fiber-optic cable. Because of the relatively high cost of this cable and its installation, fiber-optic cable should be tested both before installation (on-the-reel testing) and after installation. Continuity testing of the fiber requires either a visible light source or a reflectometer. Light sources capable of providing light at the three predominant wavelengths-850 nanometers (nm), 1300 nm, and 1550 nm-are used with power meters that can measure the same wavelengths and test attenuation and return loss in the fiber.

    TDRs and OTDRs

    At the top end of the cable testing spectrum are TDRs. These devices can quickly locate open and short circuits, crimps, kinks, sharp bends, impedance mismatches, and other defects in metallic cables.

    A TDR works by bouncing a signal off the end of the cable. Opens, shorts, and other problems reflect the signal back at different amplitudes, depending on the problem. A TDR measures how much time it takes for the signal to reflect and calculates the distance to a fault in the cable. TDRs can also be used to measure the length of a cable. Some TDRs can also calculate the propagation rate based on a configured cable length.

    Fiber-optic measurement is performed by an OTDR. OTDRs can accurately measure the length of the fiber, locate cable breaks, measure the fiber attenuation, and measure splice or connector losses. An OTDR can be used to take the signature of a particular installation, noting attenuation and splice losses. This baseline measurement can then be compared with future signatures when a problem in the system is suspected.

    Breakout Boxes, Fox Boxes, and BERTs/BLERTs

    Breakout boxes, fox boxes, and bit/block error rate testers (BERTs/BLERTs) are digital interface testing tools used to measure the digital signals present at PCs, printers, modems, the channel service unit/digital service unit (CSU/DSU), and other peripheral interfaces. These devices can monitor data line conditions, analyze and trap data, and diagnose problems common to data communication systems. Traffic from data terminal equipment (DTE) through data communications equipment (DCE) can be examined to help isolate problems, identify bit patterns, and ensure that the proper cabling has been installed. These devices cannot test media signals such as Ethernet, Token Ring, or FDDI.

    Network Monitors

    Network monitors continuously track packets crossing a network, providing an accurate picture of network activity at any moment, or a historical record of network activity over a period of time. They do not decode the contents of frames. Monitors are useful for baselining, in which the activity on a network is sampled over a period of time to establish a normal performance profile, or baseline.

    Monitors collect information such as packet sizes, the number of packets, error packets, overall usage of a connection, the number of hosts and their MAC addresses, and details about communications between hosts and other devices. This data can be used to create profiles of LAN traffic as well as to assist in locating traffic overloads, planning for network expansion, detecting intruders, establishing baseline performance, and distributing traffic more efficiently...

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