Troubleshooting DHCP Server Problems

The problems that you might encounter when you configure the server fall into the following categories:

• IP Address Allocation Errors in DHCP

IP Address Allocation Errors in DHCP

When a client attempts to obtain or verify an IP address, you might see problems logged to syslog or in server debugging mode output. The following list of common error messages indicates the possible causes and solutions.

There is no n.n.n.n dhcp-network table for DHCP client's network

Cause: A client is requesting a specific IP address or seeking to extend a lease on its current IP address. The DHCP server cannot find the DHCP network table for that address.

Solution: The DHCP network table might have been deleted mistakenly. You can recreate the network table by adding the network again using DHCP Manager or the dhcpconfig command.

ICMP ECHO reply to OFFER candidate: n.n.n.n, disabling

Cause: The IP address considered for offering to a DHCP client is already in use. This problem might occur if more than one DHCP server owns the address. The problem might also occur if an address was manually configured for a non-DHCP network client.

Solution: Determine the proper ownership of the address. Correct either the DHCP server database or the host's network configuration.

ICMP ECHO reply to OFFER candidate: n.n.n.n. No corresponding dhcp network record.

Cause: The IP address considered for offering to a DHCP client does not have a record in a network table. This error indicates that the IP address record was deleted from the DHCP network table after the address was selected. This error can only happen in the brief period before the duplicate address check is completed.

Solution: Use DHCP Manager or the pntadm command to view the DHCP network table. If the IP address is missing, create the address with DHCP Manager by choosing Create from the Edit menu on the Address tab. You can also use pntadm to create the IP address.

DHCP network record for n.n.n.nis unavailable, ignoring request.

Cause: The record for the requested IP address is not in the DHCP network table, so the server is dropping the request.

Solution: Use DHCP Manager or the pntadm command to view the DHCP network table. If the IP address is missing, create the address with DHCP Manager by choosing Create from the Edit menu on the Address tab. You can also use pntadm to create the address.

n.n.n.n currently marked as unusable.

Cause: The requested IP address cannot be offered because the address has been marked in the network table as unusable.

Solution: You can use DHCP Manager or the pntadm command to make the address usable.

n.n.n.n was manually allocated. No dynamic address will be allocated.

Cause: The client ID has been assigned a manually allocated address, and that address is marked as unusable. The server cannot allocate a different address to this client.

Solution: You can use DHCP Manager or the pntadm command to make the address usable, or manually allocate a different address to the client.

Manual allocation (n.n.n.n, client ID) has n other records. Should have 0.

Cause: The client that has the specified client ID has been manually assigned more than one IP address. A client should be assigned only one address. The server selects the last manually assigned address that is found in the network table.

Solution: Use DHCP Manager or the pntadm command to modify IP addresses to remove the additional manual allocations.

No more IP addresses on n.n.n.nnetwork.

Cause: All IP addresses currently managed by DHCP on the specified network have been allocated.

Solution: Use DHCP Manager or the pntadm command to create new IP addresses for this network.

Client: clientid lease on n.n.n.n expired.

Cause: The lease was not negotiable and timed out.

Solution: The client should automatically restart the protocol to obtain a new lease.

Offer expired for client: n.n.n.n

Cause: The server made an IP address offer to the client, but the client took too long to respond and the offer expired.

Solution: The client should automatically issue another discover message. If this message also times out, increase the cache offer time out for the DHCP server. In DHCP Manager, choose Modify from the Service menu.

Client: clientid REQUEST is missing requested IP option.

Cause: The client's request did not specify the offered IP address, so the DHCP server ignored the request. This problem might occur if you use a third-party DHCP client that is not compliant with the updated DHCP protocol, RFC 2131.

Solution: Update the client software.

Client: clientid is trying to renew n.n.n.n, an IP address it has not leased.

Cause: The IP address for this client in the DHCP network table does not match the IP address that the client specified in its renewal request. The DHCP server does not renew the lease. This problem might occur if you delete a client's record while the client is still using the IP address.

Solution: Use DHCP Manager or the pntadm command to examine the network table, and correct the client's record, if necessary. The client ID should be bound to the specified IP address. If the client ID is not bound, edit the address properties to add the client ID.

Client: clientid is trying to verify unrecorded address: n.n.n.n, ignored.

Cause: The specified client has not been registered in the DHCP network table with this address, so the request is ignored by this DHCP server.

Another DHCP server on the network might have assigned this client the address. However, you might also have deleted the client's record while the client was still using the IP address.

Solution: Use DHCP Manager or the pntadm command to examine the network table on this server and any other DHCP servers on the network. Make corrections, if necessary.

You can also do nothing and allow the lease to expire. The client automatically requests a new address lease.

If you want the client to get a new lease immediately, restart the DHCP protocol on the client by typing the following commands:

ipadm delete-addr -r dhcp-addrobj
ipadm create-addr -T dhcp dhcp-addrobj