Content

| 7.2 |  | Gathering Information on Application Layer Problems |
| 7.2.4 |  | Cisco IOS commands |

The Cisco IOS software offers powerful commands to help in monitoring and troubleshooting network problems. The following highlights some of the most common and useful commands.

- The show commands help monitor installation behavior and normal network behavior, as well as isolate problem areas.
- The debug commands assist in the isolation of protocol and configuration problems.

The router show commands are among the most important tools for understanding the status of a router, detecting neighboring routers, monitoring the network in general, and isolating problems in the network.

These commands are essential in almost any troubleshooting and monitoring situation. Use show commands for the following activities:

- Monitoring router behavior during initial installation
- Monitoring normal network operation
- Isolating problem interfaces, nodes, media, or applications
- Determining when a network is congested
- Determining the status of servers, clients, or other neighbors

The debug EXEC commands can provide a wealth of information about the traffic being seen (or not seen) on an interface, error messages generated by nodes on the network, protocol-specific diagnostic packets, and other useful troubleshooting data. Be conservative with debug commands as these commands often generate quite a bit of extraneous data.

Use debug commands to isolate problems, not to monitor normal network operation. Use debug commands to look for specific types of traffic or problems after narrowing the problems to a likely subset of causes.

Figure shows examples of IOS troubleshooting commands.