CCNA Discovery 3 - Chapter 9

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  • 1. Troubleshooting an Enterprise Network Introducing Routing and Switching in the Enterprise – Chapter 9Version 4.0 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 1
  • 2. Objectives Explain the importance of uptime and the types of issues that cause failure. Isolate and correct switching problems. Isolate and correct routing issues. Isolate and correct WAN configurations. Isolate and correct ACL issues. © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 2
  • 3. Explain the Importance of Uptime and the Types of Issues that Cause Failure Reduction in uptime can have a negative impact on a business Downtime results in lost productivity and customer frustration © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 3
  • 4. Explain the Importance of Uptime and the Types of Issues that Cause FailureWays to ensure uptime: Proactive maintenance Network monitoring © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 4
  • 5. Explain the Importance of Uptime and the Types of Issues that Cause Failure Failure domain: area of the network affected by the failure or misconfiguration of a network device Troubleshoot resources with a larger failure domain first, unless another problem is business critical © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 5
  • 6. Explain the Importance of Uptime and the Types of Issues that Cause FailureTroubleshooting approaches: Top-down Bottom-up Divide and conquer Trial and error Substitution © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 6
  • 7. Isolate and Correct Switching Problems The most common problems with switches occur at the Physical Layer © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 7
  • 8. Isolate and Correct Switching Problems Suboptimal switching can be traced to STP problems Determine the VLAN assignment of non-functioning ports Verify the trunking protocol if inter-VLAN routing is required © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 8
  • 9. Isolate and Correct Switching Problems Verify VTP domain name Verify identical revision numbers on all devices Verify identical VTP versions on all devices © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 9
  • 10. Isolate and Correct Routing IssuesDetermining and correcting RIP issues: Compatibility between RIPv1 and RIPv2 Missing or incorrect network statements Errors in interface configurations © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 10
  • 11. Isolate and Correct Routing IssuesDetermine and correct EIGRP issues: Mismatched AS numbers Errors in network statements Errors in interface addressing Auto-summarization used with discontiguous subnets © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 11
  • 12. Isolate and Correct Routing IssuesDetermine and correct OSPF issues: Mismatched authentication or timer intervals Errors in wildcard masks or network statements Errors in interface configurations © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 12
  • 13. Isolate and Correct Routing Issues Determine and correct route redistribution Verify that users on internal routers can access external networks © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 13
  • 14. Isolate and Correct WAN ConfigurationsDetermine and correct WAN Physical Layer connection issues: Clocking Cable types Loose or faulty connectors © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 14
  • 15. Isolate and Correct WAN ConfigurationsDetermine and correct WAN Data Link Layer and Network Layer connection issues: Encapsulation mismatches Incompatible formats IP addressing errors © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 15
  • 16. Isolate and Correct WAN Configurations Determine and correct authentication issues © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 16
  • 17. Isolate and Correct ACL Issues Verify network connectivity before an ACL is applied Enable logging © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 17
  • 18. Isolate and Correct ACL IssuesDetermine and correct ACL configuration and placement issues: ACL statements should permit highest volume traffic early in the ACL Implicit deny may have unintended consequences Improper ACL placement may waste bandwidth © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 18
  • 19. Summary Adherence to the three-layer hierarchical network design model assists in troubleshooting When troubleshooting a network, determine the scope of the problem and isolate the issue to a specific failure domain. The most common problems with switches occur at the Physical Layer. Use debug commands to isolate problems, not to monitor normal network operation. When troubleshooting PPP, verify that the LCP has been opened, authentication and NCP completed. ACLs can create complications in network operations. © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 19
  • 20. © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 20