The following set of commands is invaluable in both configuration and maintenance of a live network. These commands are particularly useful in troubleshooting the network. As such, these commands are a necessary set of tools for use on a daily basis, for the CCNP/CCDP Routing exam as well as the CCIE lab exam:
• show ip ospf—Shows the OSPF process and its details—for example, how many times the router has recalculated its routing table.
• show ip ospf database—Shows the contents of the topological database.
• show ip ospf interface—Gives information on how OSPF has been configured on each interface. Typing errors are easily seen with this command.
• show ip ospf neighbor—Displays all the information about the relationship that the router has with its neighbors—for example, the status of communication and whether it is initializing or transferring DDP packets.
• show ip protocols—Enables you to view the IP configuration on the router. This command is useful because it shows not only the interfaces, but the configuration of the IP routing protocols as well.
• show ip route—Shows detailed information on the networks that the router is aware of and the preferred paths to those networks. Also gives the next logical hop as the next step in the path (this command is covered in detail in Chapter 4, "IP Routing Principles").
Understanding the output of these commands is important. This is not just because the output may constitute questions on the exam, but because the capability to analyze what is happening on the network demands a thorough understanding of the concepts explained in this chapter. An understanding of the concepts in this chapter is required in interpreting the output of a show command.
The OSPF show commands are highly detailed and give a comprehensive understanding of the state of the network.
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