Troubleshooting DHCP servers

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Troubleshooting DHCP servers

What problem are you having?

• The DHCP server is stopped.

• The DHCP server is unable to provide service to clients.

• One of two DHCP servers on the same subnet is not servicing clients.

• The DHCP server appears to have suffered some data corruption or loss.

• The server appears to be affected by another problem not described above.

The DHCP server is stopped.

• Cause:  The DHCP server has not been authorized to operate on the network.

• Solution:  Authorize the DHCP server in the enterprise where it is being used.

• See also:  Authorizing DHCP servers; Authorize a DHCP server in Active Directory; Delegate ability to authorize DHCP servers to a non-enterprise administrator

• Cause:  Configuration details might be incorrect or missing at the server.

• Solution:  If you have just completed setting up or administering the DHCP server, you might want to review the provided checklist to see if you have missed a crucial step in the installation process.

  To help prevent the most common types of problems, review DHCP best practices for tips on deploying and managing your servers.

  Because many DHCP failures are first detected as client-side errors, you might want to start by investigating the problem there.

• See also:  Checklist: Installing a DHCP server; DHCP Best Practices; Troubleshooting DHCP clients

• Cause:  The DHCP server has been stopped.

• Solution:  Check the system event log and DHCP server audit log files for details.

  When the DHCP Server service either stops or cannot start, useful explanatory information about the source of the service failure or shutdown can generally be found in these logs.

• See also:  Audit logging; Analyzing server log files; Using the Event Viewer snap-in; Search for specific events

The DHCP server is unable to provide service to clients.

• Cause:  The server is a multihomed computer and is not providing service on one or more of its network connections.

• Solution:  Review Windows Server 2003 DHCP binding defaults for network connections based on whether you have elected to either statically or dynamically configure TCP/IP for any or all installed connections on the server computer. Also, review an example of multihomed DHCP server configuration to see if you have missed any critical details.

• See also:  Multihomed DHCP servers; Selectively set DHCP server bindings for network connections

• Cause:  Scopes or superscopes on the DHCP server have not been either configured or activated for use.

• Solution:  Add scopes and make sure that they are correctly configured along with any DHCP scope options that need to be assigned for client use.

• See also:  Configuring scopes; Create a new scope; Assign a scope-based option

• Cause:  The server is located on a different subnet as some of its clients and is not providing service to clients on remote subnets.

• Solution:  If you are using a DHCP server in a routed network, you might want to review issues related to DHCP relay agents and the appropriate use of superscopes.

• See also:  DHCP/BOOTP Relay Agents; Using superscopes; Create a superscope

• Cause:  The scope in use is full and can no longer lease addresses to requesting clients.

• Solution:  If the DHCP server does not have IP addresses available to provide to its clients, it returns DHCP negative acknowledgment messages (DHCPNAKs) to them. When this occurs, consider the following possible solutions:

1. Expand the address range by increasing the End IP address for the current scope.

2. Create a new additional scope and a superscope, then add the current scope and the new scope to the superscope.

3. Create a new scope or extend the range. Optimally, you could renumber your current IP network. Deactivate the old scope as needed, and then configure and activate the new one.

4. Reduce the lease duration. This can help to expedite the reclaiming of lapsed scope addresses.

   Other DHCP-related procedures and techniques might also help to accelerate or ease the transition from an existing scope being retired to a new scope created to take its place at the server. These include deleting client leases from the scope being retired, excluding addresses from that scope, and then deactivating it once the new scope has been activated. This ensures that the DHCP client obtains leasing from the new scope.

• **See also: ** Managing leases; Removing scopes; Delete a client lease; Exclude an address from a scope; Activate a scope; Deactivate a scope

• Cause:  The range of IP addresses being offered by the DHCP server is in conflict with the range of addresses being offered by another DHCP server on the network.

  You can confirm that this is the likely cause if DHCP server logs still indicate that DHCP negative acknowledgment messages (DHCPNAKs) are being returned to requesting clients or if you have tried unsuccessfully at the client to renew its lease manually.

• Solution:  Modify the scope address pool for the scopes at each DHCP server to ensure that scope IP addresses do not overlap. You can add exclusions to the scopes as necessary, delete client leases, and temporarily enable server-side conflict detection to assist in solving the problem.

• See also:  Delete a client lease; Exclude an address from a scope; Enable address conflict detection; DHCP Best Practices

One of two DHCP servers on the same subnet is not servicing clients.

• Cause:  The DHCP server is not authorized in Active Directory.

• Solution:  If the DHCP server is a domain member, authorize the server in Active Directory.

  In some circumstances you might accidentally have a standalone server and a domain member server on the same subnet. When the standalone server detects the domain member server, it attempts to verify that it is authorized in Active Directory. Even if a domain controller resides on the same subnet as the standalone DHCP server, the DHCP server cannot verify its status with the domain controller because the DHCP server is not a domain member. When the standalone server is unable to access a domain controller to discover whether it is authorized, it stops servicing clients and displays the red icon in the DHCP console that indicates the server is unauthorized. If you want the standalone server to service clients on the subnet, remove the authorized DHCP server from the subnet.

• See also:  Authorizing DHCP servers; Authorize a DHCP server in Active Directory; DHCP console icons reference

The DHCP server appears to have suffered some data corruption or loss.

• Cause:  The DHCP server database has become corrupted or is missing server data, possibly reporting JET database errors.

• Solution:  Use DHCP server data recovery options to restore the database and correct any of the reported errors. You can also use the Reconcile feature in the DHCP console to verify and reconcile any database inconsistencies that the server is able to find.

• See also:  Restoring server data; The DHCP database; Reconciling scopes; Reconcile the DHCP database; Reconcile a scope

The server appears to be affected by another problem not described above.

• Cause:  My problem is not described above.

• Solution:  Search the Microsoft Web site for updated technical information that might relate to the problem you have observed. You can obtain information and instructions that pertain to your current problem or issue.

  If you have connection to the Internet, the latest updates for members of the Windows Server 2003 family are available at the Microsoft Web site.

• See also:  DHCP updated technical information; DHCP; Using the Windows Deployment and Resource Kits; Microsoft Web site