Copyright 2003 The show ip route Command The show ip route command displays the contents of the IP routing table. This table contains entries for all known networks and subnetworks, and a code that indicates how that information was learned.
Copyright 2003 Determining the Gateway of Last Resort A default gateway is only configured when IP routing is disabled. The term gateway of last resort includes the default route, default network, and default gateway.
Copyright 2003 Configuring a Default Route router rip network network ip default-network
Copyright 2003 Determining Route Source and Destination The path-determination function enables a router to evaluate the available paths to a destination and to establish the preferred handling of a packet.
Copyright 2003 Structured Approach to Troubleshooting
Copyright 2003 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 Typical Layer 1 Errors
Copyright 2003 Improperly configured serial interfaces Improperly configured Ethernet interfaces Improper encapsulation set (HDLC is default for serial interfaces.) Improper clock rate settings on serial interfaces Typical Layer 2 Errors
Copyright 2003 Layer 1 Troubleshooting Issues Using Indicators
Copyright 2003 Layer 3 Troubleshooting Using Ping
Copyright 2003 Layer 7 Troubleshooting Using Telnet It allows verification of the application layer software between source and destination stations.
Copyright 2003 The show interfaces Command The show command used to check the status and statistics of the interfaces is the show interfaces command. Variations of this command enable you to check the status of the different types of interfaces.
Copyright 2003 Troubleshooting Layer 2 with the show interfaces Command If the interface is up and the line protocol is down, a Layer 2 problem exists. Among the possible causes are the following: –No keepalives –No clock rate –Mismatch in encapsulation type
Copyright 2003 The show controllers serial Command By examining the show controllers serial command output, the type of cable that the controller detects can be determined. This is useful for finding a serial interface with no cable, the wrong type of cable, or a defective cable.