IPCONFIG is one of the most useful little utilities on your computer (for Windows systems), especially for helping you to debug network issues. IPCONFIG can be used to show your current TCP/IP information, including your address, DNS server addresses, adapter type and so on.

This is most useful if you are using DHCP (a method to automatically assign TCP/IP information needed by a computer). Since the TCP/IP information, including the address, is assigned when the computer is booted, it is not known until boot time. IPCONFIG will show that information at any time.

C:\>IPCONFIG/ALL   Windows IP Configuration   Host Name . . . . . . . . . . . . : TEST Primary Dns Suffix . . . . . . . : Node Type . . . . . . . . . . . . : Hybrid IP Routing Enabled. . . . . . . . : No WINS Proxy Enabled. . . . . . . . : No   Ethernet adapter Local Area Connection:   Connection-specific DNS Suffix . : mynetwork.com Description . . . . . . . . . . . : CNet PRO200WL PCI Fast Ethernet Physical Address. . . . . . . . . : 00-08-A1-2A-DB-26 Dhcp Enabled. . . . . . . . . . . : Yes Autoconfiguration Enabled . . . . : Yes IP Address. . . . . . . . . . . . : 192.168.100.8 Subnet Mask . . . . . . . . . . . : 255.255.255.0 Default Gateway . . . . . . . . . : 192.168.100.1 DHCP Server . . . . . . . . . . . : 192.168.168.1 DNS Servers . . . . . . . . . . . : 205.166.226.38 206.13.30.12 Lease Obtained. . . . . . . . . . : Sunday, October 27, 2002 8:35:42 PM Lease Expires . . . . . . . . . . : Sunday, October 27, 2002 9:35:42 PM   C:\>

To use IPCONFIG, specify IPCONFIG at the CMD prompt. You can optionally follow the command with one or more of the following qualifiers.

/ALL

This causes all of the TCP/IP configuration information to be displayed for all adapters. These may include network and dial-up adapters.

/RENEW [adapter-name]

If your system is configured to use DHCP, then this qualifer will ask the DHCP server for new configuration information. Using the "adapter-name" option renews the DHCP for the specified adapter.

/RELEASE [adapter-name]

If your system uses DHCP, then this qualifier asks the DHCP server to release the DHCP configuration and discard the TCP/IP address. If "adapter-name" is included, then only the address for the specified adapter is discarded.

/FLUSHDNS

As DNS information is requested from the DNS servers, it is cached locally so that it does not have to be requested again. This qualifier deletes all of the information in that cache.

/DISPLAYDNS

This qualifier displays all of the information in the local DNS cache. This includes information from the HOSTS file and any recently obtained DNS entries.

/REGISTERDNS

Requests a manual dynamic registration for the DNS names and TCP/IP addresses that are configured at your computer. This can be used to troubleshoot a failed DNS name registration (by asking for it again).

/SHOWCLASSID adapter-name

Use this qualifier to show the DHCP class ID for the specified adapter. You can use the wildcard character (*) to show all adapters.

/SETCLASSID adapter-name [classid]

Sets the DHCP class id for a specified adapter. You can use the wildcard character (*) to set all adapters.