Troubleshooting Tip: Failure to create DHCP reservation within same subnet/netmask on DHCP monitor

[jera]

Description	This article describes the issue of creating a DHCP reservation within the same subnet.
Scope	FortiGate v7.4.9/v7.6.4.
Solution	Users may encounter an error: 'Http failure response for https://<FortiGate IP>/api/v2/cmdb/system.dhcp/server/2/reserved-address?vdom=root: 500 OK' when trying to reserve an IP on a DHCP netmask configured on FortiGate.  This is a known issue reported on versions 7.4 and 7.6, with bug ID 1169825 failed to create a DHCP reservation within the same subnet/netmask on the DHCP monitor. This will be permanently fixed on v7.6.5. A workaround is to manually create the dhcp reservation on the FortiGate interface. Refer to Technical Tip: How to set DHCP IP reservation on FortiGate’s interface. Diagram: FortiGate (DHCP server - port 2) ---- (DHCP client port 2). DHCP Configuration on FortiGate Interface.