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Chapter 8 TCP/IP Suite Error and Control Messages/ Basic Router Troubleshooting

Chapter 8 TCP/IP Suite Error and Control Messages/ Basic Router Troubleshooting. Objectives. Internet Control Message Protocol (ICMP). Error Reporting and Error Correction. ICMP is an error - reporting protocol for IP. ICMP Message Delivery.

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Chapter 8 TCP/IP Suite Error and Control Messages/ Basic Router Troubleshooting

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  1. Chapter 8TCP/IP Suite Error and Control Messages/ Basic Router Troubleshooting

  2. Objectives

  3. Internet Control Message Protocol (ICMP)

  4. Error Reporting and Error Correction • ICMP is an error-reporting protocol for IP.

  5. ICMP Message Delivery • ICMP messages are encapsulated as data in datagrams in the same way any other data is delivered using IP.

  6. Unreachable Networks

  7. Ping

  8. Detecting Excessively Long Routes • Whether the actual path includes too many hops or a circular routing path exists, the packet will eventually reach the end of its life, known as its time-to-live (TTL).

  9. ICMP Message Types

  10. Destination Unreachable Message

  11. Code Values for Destination Unreachable Messages

  12. TCP/IP Suite Control Messages • Control messages are used to inform hosts of conditions such as network congestion or the existence of a better gateway to a remote network.

  13. ICMP Redirect/Change Requests The default gateway of the host may need to use a redirect/change request to inform the host of the best path to a certain network.

  14. Clock Synchronization and TransitTime Estimation • The ICMP timestamp request message allows a host to ask for the current time according to the remote host. • The remote host uses an ICMP timestamp reply message to respond to the request.

  15. Address Mask Requirements • When a network administrator uses the process of subnetting to divide a major IP address into multiple subnets, a new subnet mask is created.

  16. Router Discovery Message • When a host on the network boots, and the host has not been manually configured with a default gateway, it can learn of available routers through the process of router discovery.

  17. Router Solicitation Message • A host generates an ICMP router solicitation message in response to a missing default gateway.

  18. Congestion and Flow Control Messages ICMP source-quench messages are used to reduce the amount of data lost from congestion.

  19. Summary

  20. Basic Router Troubleshooting

  21. Objectives

  22. The show ip route Command The show ip route command displays the contents of the IP routing table.

  23. Static Routing

  24. Dynamic Routing

  25. Default Route

  26. Configuring a Default Route

  27. Determining Route Source and Destination

  28. Determining L2 and L3 Addresses

  29. Determining Administrative Distance

  30. Determining the Route Metric Routing protocols use metrics to determine the best route to a destination.

  31. Determining the Route Next Hop • Destination next hop associations determine the best path and which router to forward the packet to next. This router represents the next hop on the way to the final destination.

  32. Determining the Last Routing Update • Use the following commands to find the last routing update: • show ip route • show ip route network • show ip protocols • show ip rip database

  33. Observing Multiple Paths to a Destination • Some routing protocols support multiple paths to the same destination. • Unlike single path algorithms, these multi-path algorithms permit traffic over multiple lines, provide better throughput, and are more reliable.

  34. Introduction to Network Testing

  35. Structured Approach to Troubleshooting

  36. Typical Layer 1 Errors • Broken cables • Disconnected cables • Cables connected to the wrong ports • Intermittent cable connection • Wrong cables used for the task at hand • Transceiver problems • DCE cable problems • DTE cable problems • Devices turned off

  37. Typical Layer 2 Errors • Improperly configured serial interfaces • Improperly configured Ethernet interfaces • Improper encapsulation set • Improper clock rate settings on serial interfaces • Network interface card (NIC) problems

  38. Typical Layer 3 Errors • Routing protocol not enabled • Wrong routing protocol enabled • Incorrect IP addresses • Incorrect subnet masks

  39. Layer 1 Problems in a Network

  40. Layer 3 Troubleshooting Using Ping

  41. Layer 7 Troubleshooting Using Telnet

  42. Troubleshooting Layer 1 Using show interfaces Command The show interfaces serial command

  43. Troubleshooting Layer 2 Usingshow interfaces Command

  44. Troubleshooting Using show cdp neighbors Command

  45. Troubleshooting Using show cdp neighbors detail Command

  46. Troubleshooting Usingtraceroute Command

  47. Troubleshooting Routing Issues The show ip route Command

  48. Troubleshooting Routing Issues The show ip protocols Command

  49. Troubleshooting Using show controllers serial Command The show controllers serial Command

  50. Introduction to debug Debug syntax

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