IPCONFIG

Configure IP (Internet Protocol configuration)

Syntax

   IPCONFIG /all          Display full configuration information.

   IPCONFIG /release [adapter]
                          Release the IP address for the specified adapter.

   IPCONFIG /renew [adapter]
                          Renew the IP address for the specified adapter.

   IPCONFIG /flushdns     Purge the DNS Resolver cache.

   IPCONFIG /registerdns  Refresh all DHCP leases and re-register DNS names.

   IPCONFIG /displaydns   Display the contents of the DNS Resolver Cache.

   IPCONFIG /showclassid adapter
                          Display all the DHCP class IDs allowed for adapter.

   IPCONFIG /setclassid adapter [classid]
                          Modify the dhcp class id.

If the Adapter name contains spaces, use quotes: "Adapter Name"
Wildcard characters * and ? are allowed, see the examples below

The default is to display only the IP address, subnet mask and default gateway for each adapter bound to TCP/IP.

For Release and Renew, if no adapter name is specified, then the IP address leases for all adapters bound to TCP/IP will be released or renewed.

If you remote into a computer and run ipconfig /release it will kill your connection

For setclassid, if no CLASS ID is specified, then the CLASS ID is removed.

DHCP User Classes allow additional or modified DHCP options to be applied to a subset of computers on the network, as identified by a CLASS ID. For example, a different gateway, DNS server, or lease time.
This requires configuring the CLASS ID appropriately on the DHCP server. see RFC 3004

Examples:

Show detailed information
C:\> ipconfig /all

Release and Renew all adapters:
ipconfig /release
ipconfig /renew

Release and Renew all adapters - one liner for remote use:
ipconfig /release && ipconfig /renew

Renew any connection that has a name starting with EL:
ipconfig /renew EL*

Release all connections matching *Con*, eg. "Local Area Connection 1" or "Local Area Connection 2":
ipconfig /release *Con*

Set the DHCP class ID for the named adapter to TEST:
ipconfig /setclassid "Local Area Connection" TEST

“Life is a grand adventure - or it is nothing” ~ Helen Keller

Related:

BROWSTAT - Get domain, browser and PDC info.
NETSTAT - Display networking statistics (TCP/IP).
NETSH - Configure interfaces, routing protocols, filters, routes, RRAS.
PATHPING - IP trace utility.
PING - Test a network connection.
Q813878 - How to block specific network protocols and ports.
Q313190 - Use IPSec IP Filter Lists.
TechNet Domain Name System - How DNS works.
ipchicken - Display your current IP.
Equivalent bash command (Linux): lookupd -flushcache, ifconfig - IP configuration.
Equivalent PowerShell command: Clear-DnsClientCache - Clear the content of the DNS client cache.
Equivalent bash command (OS X): ipconfig / dscacheutil - View IP config / Query / flush the Directory Service cache.