TCP/IP Troubleshooting

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Check Configuration with IPConfig

When troubleshooting a TCP/IP networking problem, begin by checking the TCP/IP configuration on the computer experiencing the problem. Use the ipconfig command to get the host computer configuration information, including the IP address, subnet mask, and default gateway.

When Ipconfig is used with the /all switch, it produces a detailed configuration report for all interfaces, including any configured remote access adapters. Ipconfig output may be redirected to a file and pasted into other documents. To do so, type ipconfig > <directory\file name>. The output is placed in the directory you specified with the file name you specified.

The output of Ipconfig can be reviewed to find any problems in the computer network configuration. For example, if a computer has been configured with an IP address that is a duplicate of an existing IP address that has already been detected, the subnet mask appears as 0.0.0.0.

The following example illustrates the results of an ipconfig /all command on a computer that is configured to use a DHCP server for automatic TCP/IP configuration, and WINS and DNS servers for name resolution:

Windows NT IP Configuration

Host Name . . . . . . . . . : testpc1.reskit.com

Node Type . . . . . . . . . : Hybrid

IP Routing Enabled. . . . . : No

WINS Proxy Enabled. . . . . : No


Ethernet adapter Local Area Connection:

Adapter Domain Name . . . . : dns.reskit.com

DNS Servers . . . . . . . . : 172.16.14.119

Description . . . . . . . . : ELNK3 Ethernet Adapter.

Physical Address. . . . . . : 00-20-AF-1D-2B-91

DHCP Enabled. . . . . . . . : Yes

IP Address. . . . . . . . . : 172.16.48.10

Subnet Mask . . . . . . . . : 255.255.248.0

Default Gateway . . . . . . : 172.16.48.03

DHCP Server . . . . . . . . : 172.16.48.03

Primary WINS Server . . . . : 172.16.48.04

Secondary WINS Server . . . : 172.16.48.05

Lease Obtained. . . . . . . : Sunday, May 2, 1999 11:43:01 PM

Lease Expires . . . . . . . : Wednesday, May 5, 1999 11:43:01 PM


If no problems appear in the TCP/IP configuration, the next step is to test the ability to connect to other host computers on the TCP/IP network.

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