ERF12-6899 [ProxyAPI::ProxyException]: Unable to set DHCP entry ([RestClient::BadRequest]: 400 Bad Request) for proxy

Environment

• Red Hat Satellite 6.x
• PXE-based provisioning

Issue

• Creating new host using additional subnet on Red Hat Satellite 6.x fails with below error.

Create DHCP Settings for client.example.com task failed with the following error: ERF12-6899 [ProxyAPI::ProxyException]: Unable to set DHCP entry ([RestClient::BadRequest]: 400 Bad Request) for proxy https://capsule.example.com:9090/dhcp

Unable to save
Create DHCP Settings for client.example.com task failed with the following error: ERF12-6899 [ProxyAPI::ProxyException]: Unable to set DHCP entry ([RestClient::BadRequest]: 400 Bad Request) for Capsule https://satellite.example.com:9090/dhcp

Resolution

There is a DHCP host reservation that already exists for the particular hostname. Check the DHCP database on the Capsule that is causing the error (
/var/lib/dhcpd/dhcpd.leases):

host host123.example.com {
  dynamic;
  hardware ethernet 00:50:56:cc:bb:aa;
  fixed-address 192.168.99.100;
  supersede server.filename = "pxelinux.0";
  supersede server.next-server = 0a:c1:20:10;
  supersede host-name = "host123.example.com";
}

In order to fix this error, delete the problematic record. Please read the manual page for dhcpd.leases about the format of this file, it's append only. Create a backup of the lease file before proceeding.

• The first option is to delete a record is to append deletion entry:

cat >> /var/lib/dhcpd/dhcpd.leases <<EOA
host host123.example.com {
  dynamic;
  deleted;
}
EOA

• The second option is to stop dhcpd daemon, delete the entry in /var/lib/dhcpd/dhcpd.leases and start it again.

Additional checklist to prevent the issue happen:

• Do not associate or change Subnet for existing hosts. The correct workflow is to delete the host and create a new one. Only change Subnets when you follow with manual edits of configuration files. This applies to Domains.

• Do not change TFTP, DHCP and DNS proxies for existing Subnet or Domain objects when there are existing hosts. This will again lead to inconsistency.

• Make sure all the Red Hat Satellite 6 is configured correctly for This content is not included.provisioning.

• When executing katello-installer with DHCP, DNS & other parameters as per This content is not included.provisioning guide at the initial Red Hat Satellite installation step, the DNS entry for primary subnet is created. But for additional subnet it is required to manually add the entry in /etc/zones.conf file and create the subnet file under /var/named/dynamic similar to primary subnet.

• If you notice the error after upgrade, verify that no custom configuration in /etc/dhcp/dhcpd.conf overwritten by installer.
  See Applying custom configuration to your Satellite article for more information.
  Also, make sure to restart foreman-proxy and dhcpd services when you restore old dhcpd.conf configuration as per the article.

• Make sure you are provisioning in the same subnet for which you are running your dhcp services as defined in /etc/dhcp/dhcpd.conf file.

• In case you are provisioning with more than one interface, then make sure the subnet for the non-provisioning interface does not have a DHCP CAPSULE selected.

For more KB articles/solutions related to Red Hat Satellite 6.x Provisioning Issues, please refer to the Consolidated Troubleshooting Article for Red Hat Satellite 6.x Provisioning related Issues

Root Cause

This can happen when you create new host, then undefine Subnet from it and then delete it. Then Satellite 6 will not delete the reservation apparently because the Subnet was already undefined. Future version of Satellite 6 will show a warning, but we want to keep the possibility to change the Subnet for advanced users.

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