IPConfig is a command-line tool that displays the current configuration of the installed IP stack on a networked computer.
When used with the
/all
switch, it displays a detailed configuration report for all interfaces, including any configured WAN miniports (typically used for remote access or VPN connections). Output can be redirected to a file and pasted into other documents. A sample report is shown here:
C:>\ipconfig /all
Windows 2000 IP Configuration
Host Name . . . . . . . . . . . . : TESTPC1
Primary DNS Suffix . . . . . . . : reskit.com
Node Type . . . . . . . . . . . . : Hybrid
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No
DNS Suffix Search List. . . . . . : ntcorpdc1.reskit.com
dns.reskit.com
reskit.com
Ethernet adapter Local Area Connection:
Connection-specific DNS Suffix . : dns.reskit.com
Description . . . . . . . . . . . : Acme XL 10/100Mb Ethernet NIC
Physical Address. . . . . . . . . : 00-CC-44-79-C3-AA
DHCP Enabled. . . . . . . . . . . : Yes
IP Address. . . . . . . . . . . . : 172.16.245.111
Subnet Mask . . . . . . . . . . . : 255.255.248.0
Default Gateway . . . . . . . . . : 172.16.240.1
DHCP Server . . . . . . . . . . . : 172.16.248.8
DNS Servers . . . . . . . . . . . : 172.16.55.85
172.16.55.134
172.16.55.54
Primary WINS Server . . . . . . . : 172.16.248.10
Secondary WINS Server . . . . . . : 172.16.248.9
Lease Obtained. . . . . . . . . . : Friday, May 05, 1999 2:21:40 PM
Lease Expires . . . . . . . . . . : Monday, May 07, 1999 2:21:40 PM
A number of other useful parameters for Ipconfig include
/flushdns
, which deletes the DNS name cache;
/registerdns
, which refreshes all DHCP leases and re-registers DNS names; and
/displaydns
which displays the contents of the DNS resolver cache.
The
/release
<
adapter
> and
/renew
<
adapter
> options release and renew the DHCP-allocated IP address for a specified adapter. If no adapter name is specified, the DHCP leases for all adapters bound to TCP/IP are released or renewed.
For
/setclassid
, if no class ID is specified, then the Class ID is removed. Table 3.3 lists all Ipconfig switches.
Table 3.3 Ipconfig Switches
|
Switch |
Effect |
|
/all |
Produces a detailed configuration report for all interfaces. |
|
/flushdns |
Removes all entries from the DNS name cache. |
|
/registerdns |
Refreshes all DHCP leases and reregisters DNS names |
|
/displaydns |
Displays the contents of the DNS resolver cache. |
|
/release <
adapter
> |
Releases the IP address for a specified interface. |
|
/renew <
adapter
> |
Renews the IP address for a specified interface. |
|
/showclassid <
adapter
> |
Displays all the DHCP class IDs allowed for the adapter specified. |
|
/setclassid <
adapter
> <
classID to set
> |
Changes the DHCP class ID for the adapter specified. |
|
/? |
Displays this list. |
The /showclassid and /setclassid options allow you to manipulate user class IDs from the command line. The user class IDs are options that a system administrator may set on the DHCP server to configure a client computer to identify itself with the server. Issuing the command
ipconfig /showclassid
<
adapter
> sends a query to the client's server; the server responds by providing the available classes. Once you know which classes are available, you can issue a command like
ipconfig /setdhcpclassid
<
adapter
> <
class ID to set on the server
> to set the class ID that the client will use from that point on. For more information about DHCP and class IDs, see
"Dynamic Host Configuration Protocol"
in this book.