Refreshing configuration by using ipconfig /renew

 

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When you troubleshoot a TCP/IP networking problem, begin by checking the TCP/IP configuration on the computer that is experiencing the problem. If the computer is DHCP-enabled and is using a DHCP server to obtain configuration, you can initiate a refresh of the lease by using the ipconfig /renew command.

When you use ipconfig /renew, all network adapters on the computer that uses DHCP (except those that are manually configured) try to contact a DHCP server and renew their existing configuration or obtain a new configuration.

You can also use the ipconfig command with the /release option to immediately release the current DHCP configuration for a host. For more information about DHCP and the lease process, see How clients obtain configuration

 Note

• For Windows 95 and Windows 98 DHCP-enabled clients, use the release and renew options of the winipcfg command instead of ipconfig /release and ipconfig /renew to perform manual release or renewal of the IP configuration lease for a client.

Managing DNS and DHCP class IDs by using ipconfig

 

You can also use the ipconfig command to:

 

Display or reset the DNS cache - Using ipconfig to view or reset a client resolver cache

 

To flush and reset a client resolver cache using the ipconfig command

• At a command prompt, type:

  ipconfig /flushdns

 Note

• To open a command prompt, click Start, point to Programs, point to Accessories, and then click Command Prompt.
• The ipconfig /flushdns command provides you with a means to flush and reset the contents of the DNS client resolver cache. During DNS troubleshooting, if necessary, you can use this procedure to discard negative cache entries from the cache, as well as, any other dynamically added entries.
• Resetting the cache does not eliminate entries that are preloaded from the local Hosts file. To eliminate those entries from the cache, remove them from this file. For more information, see Related Topics.
• Although the ipconfig command is provided for earlier versions of Windows, the /flushdns option is only available for use at computers running Windows 2000 The DNS Client service must also be started.

 

 

 

Refresh registered DNS names - Using ipconfig to renew DNS client registration

 

To renew DNS client registration using the ipconfig command

• At a command prompt, type:

  ipconfig /registerdns

  Or, type ipconfig /registerdns [adapter]

  Where adapter is the name of a specific network adapter installed on the computer for which you want to renew or update registrations.

 Note

• To open a command prompt, click Start, point to Programs, point to Accessories, and then click Command Prompt.
• The ipconfig /registerdns command provides you with a means to manually initiate dynamic registration for the DNS names and IP addresses configured at a computer. This option can assist in troubleshooting a failed DNS name registration or in resolving a dynamic update problem between a client and the DNS server without requiring a client reboot.
• By default, the ipconfig /registerdns command refreshes all DHCP address leases and registers all related DNS names configured and used by the client computer.
• To learn the names of adapters that you can optionally specify with this command, first type the ipconfig command by itself (that is, do not specify any additional parameters). The command output displays all adapters by name that are available for use at the computer.
• Although the ipconfig command is provided for earlier versions of Windows, the /registerdns option is only available for use at computers running Windows 2000 with the DHCP Client service started.
• For Windows 2000, the DHCP Client service is used to perform dynamic registrations and updates, regardless of whether the computer uses a DHCP server or static configuration to obtain its IP address.
• If you are troubleshooting a failed DNS dynamic registration for a client computer and its DNS names, it might help to verify that the cause is not related to one of the following commonly known causes for such failures:
  1. The zone where the client requires update or registration is not able to accept dynamic updates.
  2. The DNS servers that the client is configured to use do not support or recognize the DNS dynamic update protocol.
  3. The primary (or directory-integrated) DNS server for the zone refused the update request. This can most likely occur because the client is not permitted under current zone or resource records security sufficient access rights to update its own name.
  4. The server or zone is not available because of other problems, such as a network or server failure.

 

Display the DHCP class IDs for an adapter - To show DHCP class ID information at a client computer

 

To show DHCP class ID information at a client computer

1. At a DHCP-enabled client computer running Windows 2000, open a command prompt
2. Use the Ipconfig command-line utility to show the DHCP class ID that the client uses when obtaining its lease from the DHCP server.

   You can type the ipconfig /showclassid command as demonstrated in the following example command. This example shows an ASCII string ("MyNewClassId") that is currently set as the DHCP class ID for the local area network connection at the client computer:

   C:\>ipconfig /showclassid "Local Area Connection"
   
   Windows 2000 IP Configuration
   
   DHCP Class ID for Adapter "Local Area Connection":
   
   DHCP ClassID Name . . . . . . . . : Default BOOTP Class
   DHCP ClassID Description  . . . . : User class for BOOTP clients
   DHCP ClassID Name . . . . . . . . : Default Remote Access Class 
   DHCP ClassID Description  . . . . : User class for remote access clients
   
   Host Name . . . . . . . . . . . . : HOSTA
   Primary DNS Suffix  . . . . . . . : example.microsoft.com
   Node Type . . . . . . . . . . . . : Hybrid
   IP Routing Enabled. . . . . . . . : No
   WINS Proxy Enabled. . . . . . . . : No
   
   Ethernet adapter Local Area Connection:
   
   Connection-specific DNS Suffix  . :
   Description . . . . . . . . . . . : Combo PCMCIA EthernetCard
   Physical Address. . . . . . . . . : 00-00-00-00-7C-DC
   DHCP Enabled. . . . . . . . . . . : Yes
   Autoconfiguration Enabled . . . . : Yes
   IP Address. . . . . . . . . . . . : 10.0.0.51
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Default Gateway . . . . . . . . . : 10.0.0.1
   DHCP Class ID . . . . . . . . . . : MyNewClassId
   DNS servers . . . . . . . . . . . : 10.0.0.3
   Primary WINS server . . . . . . . : 10.0.0.5
   

 Note

• For a DHCP options class to be in effect between the DHCP server and its clients, both must be configured with a matching DHCP class ID string that identifies the client as a member of a specific user or vendor options class when it obtains its address lease from the server.
• For more information, see Related Topics

 

Set the DHCP class IDs for an adapter - To set DHCP class ID information at a client computer

 

To set DHCP class ID information at a client computer

1. At a DHCP-enabled client computer running Windows 2000, open a command prompt
2. Use the Ipconfig command-line utility to set the DHCP class ID the client uses when obtaining its lease from the DHCP server.

   You can type the ipconfig /setclassid command as demonstrated in the following example command, which sets an ASCII string ("MyNewClassId") as the DHCP class ID string for the local area network connection in use at the client computer:

   C:\>ipconfig /setclassid "Local Area Connection" MyNewClassId
   
   Windows 2000 IP Configuration
   
   DHCP ClassId successfully modified 
   		for adapter"Local Area Connection"
   

 Note

• For a DHCP options class to be in effect between the DHCP server and its clients, both must be configured with a matching DHCP class ID string that identifies the client as a member of a specific user or vendor options class when it obtains its address lease from the server.
• For more information, see Related Topics.