Outline

Modules: | 1 | 2 | 3 | 4 | 5 | 6 | 7 | All |

Module 4: Layer 2 Troubleshooting

Module Overview |

4.1

Characteristics of Data Link Layer Problems

4.1.1 | Data link layer problems overview
4.1.2 | No component above the data link layer is functional
4.1.3 | The network is functional, but operating at less than the baseline level
4.1.4 | Framing errors
4.1.5 | Encapsulation errors
4.1.6 | Layer 2 to Layer 3 address mapping errors
4.1.7 | Critical characteristics – no network layer connectivity
4.1.8 | Upper layer component operation
4.1.9 | Critical characteristics – console messages

4.2

End-System Commands for Gathering Data Link Information

4.2.1 | Common end-system commands
4.2.2 | Microsoft Windows end-system commands
4.2.3 | UNIX/Mac operating systems end-system commands
4.2.4 | General Cisco IOS commands
4.2.5 | Cisco IOS show commands
4.2.6 | The show cdp neighbors command

4.3

Troubleshooting Switched Ethernet Networks

4.3.1 | Troubleshooting the Spanning Tree Protocol
4.3.2 | Troubleshooting STP loops
4.3.3 | Preventing STP loops
4.3.4 | Troubleshooting incorrect STP root configuration
4.3.5 | Troubleshooting Ethernet broadcast traffic
4.3.6 | Troubleshooting Ethernet switch flooding
4.3.7 | Troubleshooting VTP misconfiguration
4.3.8 | Troubleshooting EtherChannel

4.4

Troubleshooting ISDN

4.4.1 | T1 framing errors
4.4.2 | Troubleshooting ISDN primary rate switch types
4.4.3 | Troubleshooting ISDN BRI to telco communications
4.4.4 | Troubleshooting ISDN BRI dialer problems
4.4.5 | Debugging ISDN call setup failures

4.5

Troubleshooting Frame Relay

4.5.1 | Steps for troubleshooting Frame Relay
4.5.2 | The show frame-relay lmi command
4.5.3 | The show frame-relay pvc command
4.5.4 | Frame Relay encapsulation type
4.5.5 | Troubleshooting Frame Relay using the line status
4.5.6 | Ping the local IP address on a multipoint Frame Relay
4.5.7 | Reconfiguring a subinterface

4.6

PPP and Layer 2 Considerations for Routed and Routing Protocols

4.6.1 | Link Control Protocol
4.6.2 | Troubleshooting PPP authentication PAP
4.6.3 | Troubleshooting PPP authentication CHAP
4.6.4 | IP split horizon checking
4.6.5 | OSPF in an NBMA environment
4.6.6 | The keyword broadcast
4.6.7 | Excessive fragmentation

Module Summary |
Module Quiz |

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