Troubleshooting Tip: Error 'Invalid DHCP Range. Start Address Is Greater Than End Address.' when Creating DHCP IP Reservations on FortiGate GUI

The error 'Invalid DHCP range. Start address is greater than end address.' occurs when attempting to create or add IP Address Assignment Rules under DHCP Server via GUI.

This issue has been resolved in FortiOS version 7.6.1.

Workaround: Use CLI to add the IP assignment rule rule.
See this article.

Logs required by FortiGate TAC for investigation.

1. Debugs:

diagnose debug application httpsd -1
diagnose debug console timestamp enable
diagnose debug enable
<reproduce the issue>
diagnose debug reset

2. TAC Report:

execute tac report

3. Configuration file of the FortiGate.

4. Fortinet Support Tool data.