Common Problems

This section describes some of the more common problems you may encounter with DHCP, and what to do about them.

Problem

The DHCP client is sending out DHCPDISCOVER or DHCPREQUEST messages, but the DHCP server is not responding.

Verification: Check the server machine's console. It may not have any IP addresses left to allocate.

Solution: Add more IP addresses.

Verification: Check the server machine's console. If the server is stating that the client is unrecognized, then the DHCP server's databases may have been flushed, with the result that the server fails to recognize the client.

Solution: Remove any DHCP cache file on the client.

1. Interrupt the boot by typing Control -C.

2. Remove the cache by typing:

   cd /etc/dhcp; rm interface_name.dhc

3. Restart the initialization process by typing

   ifconfig interface_name dhcp release

Verification: Check the server machine's console. Perhaps support for the client's network has not been added to the DHCP databases.

Solution: Add support for the client's network, using dhcpconfig.

Verification: The client is on a network separate from that of the DHCP server, and a BOOTP relay agent has not been installed or configured.

Solution: Install and configure a BOOTP relay agent. In addition, you may need to add an entry to the netmasks(4) database for the remote network.

Problem

The client logs a message that the address is already in use.

Verification: Check whether the address is in use elsewhere. If the client continues to log the same message, it is likely that the server is not checking the address, or is ignoring the client's message which declines the address. Check to be sure you are not using the in.dhcpd command with the n option.

Solution: Find out whether the server gave out the bad address. Either the server is malfunctioning, or another user has illicitly used the same address.

Problem

The following error message is displayed:

DHCP renewal on interface_name failed

Verification: The DHCP client was unable to renew a lease on the specified interface.

Solution: Make sure that the DHCP server is still running correctly.

Problem

The following message is displayed:

Address of interface name has changed

Verification: The address or status of the interface is not what the DHCP agent expects to see. The address was probably altered manually.

Solution: There is no solution. The agent will stop trying to configure the interface.