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proc_troubleshooting-dhcp-problems.adoc

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Troubleshooting DHCP Problems in {Project}

{Project} can manage an ISC DHCP server on internal or external DHCP {SmartProxy}. {Project} can list, create, and delete DHCP reservations and leases. However, there are a number of problems that you might encounter on occasions.

Out of sync DHCP records

When an error occurs during DHCP orchestration, DHCP records in the {Project} database and the DHCP server might not match. To fix this, you must add missing DHCP records from the {Project} database to the DHCP server and then remove unwanted records from the DHCP server as per the following steps:

Procedure

  1. To preview the DHCP records that are going to be added to the DHCP server, enter the following command:

    # foreman-rake orchestration:dhcp:add_missing subnet_name=NAME

  2. If you are satisfied by the preview changes in the previous step, apply them by entering the above command with the perform=1 argument:

    # foreman-rake orchestration:dhcp:add_missing subnet_name=NAME perform=1

  3. To keep DHCP records in {Project} and in the DHCP server synchronized, you can remove unwanted DHCP records from the DHCP server. Note that {Project} assumes that all managed DHCP servers do not contain third-party records, therefore, this step might delete those unexpected records. To preview what records are going to be removed from the DHCP server, enter the following command:

    # foreman-rake orchestration:dhcp:remove_offending subnet_name=NAME

  4. If you are satisfied by the preview changes in the previous step, apply them by entering the above command with the perform=1 argument:

    # foreman-rake orchestration:dhcp:remove_offending subnet_name=NAME perform=1
PXE loader option change

When the PXE loader option is changed for an existing host, this causes a DHCP conflict. The only workaround is to overwrite the DHCP entry.

This is a known issue. Until Issue 27877 is fixed, the only workaround is to overwrite the DHCP entry.

Incorrect permissions on DHCP files

An operating system update can update the dhcpd package. This causes the permissions of important directories and files to reset so that the DHCP {SmartProxy} cannot read the required information.

For more information, see ERF12-6899 - Unable to set DHCP entry.

Changing the DHCP {SmartProxy} entry

{Project} manages DHCP records only for hosts that are assigned to subnets with a DHCP {SmartProxy} set. If you create a host and then clear or change the DHCP {SmartProxy}, when you attempt to delete the host, the action fails.

If you create a host without setting the DHCP {SmartProxy} and then try to set the DHCP {SmartProxy}, this causes DHCP conflicts.

Deleted hosts entries in the dhcpd.leases file

Any changes to a DHCP lease are appended to the end of the dhcpd.leases file. Because entries are appended to the file, it is possible that two or more entries of the same lease can exist in the dhcpd.leases file at the same time. When there are two or more entries of the same lease, the last entry in the file takes precedence. Group, subgroup and host declarations in the lease file are processed in the same manner. If a lease is deleted, { deleted; } is appended to the declaration.