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| 7.2 |  | Gathering Information on Application Layer Problems |
| 7.2.3 |  | Platform specific TCP/IP utilities |

The traffic requirements of various platforms influences how network devices are configured. Five situations where traffic requirements would affect router setup are shown in Figure .

TCP/IP troubleshooting combines facts gathered from network devices such as routers and switches, and facts gathered from a client or server.

To check the local host configuration on a Windows NT/2000/XP system, open a DOS command window on the host and enter the ipconfig /all command. The resulting output displays the TCP/IP address configuration, default gateway, DHCP server, and Domain Name System (DNS) server addresses. If any IP addresses are incorrect or if no IP address is displayed, determine the correct IP address and edit it or enter it for the local host.

The Windows NT/2000/XP platform will log most incorrect IP address or subnet mask errors in the Event Viewer. Examine the Event Viewer system log and look for any entry with TCP/IP or DHCP as the source. Read the appropriate entries by double-clicking them. Because DHCP configures TCP/IP remotely, DHCP errors cannot be corrected from the local computer.

Also, check the configurations on the NT/2000/XP server. If a connection using an IP address is possible but the connection cannot be made using Microsoft networking (for example, Network Neighborhood), try to isolate a problem with the Windows NT/2000/XP server configuration. Problem areas with Microsoft networking relate to NetBIOS support and associated mechanisms used to resolve non-IP entities with IP addresses. Non-IP problems can be checked using the nbtstat command.

As a last resort, try rebooting the Windows system. Although this practice is not encouraged, it frequently repairs the problem.

Figure shows some general commands used for isolating application layer problems. While many of these commands display lower layer information, the commands are still useful because they highlight problems in the application layer.

Figure shows the output of the ifconfig command.