Technical Tip: OSPF Graceful restart not sending Opaque LSA when executing the command 'execute router clear ospf'

[nalexiou]

Description	This article describes the behavior when the command 'execute router clear ospf' is executed and a graceful restart is configured.
Scope	FortiGate.
Solution	The graceful restart (as described in Technical Tip: Configuring FortiGate HA and OSPF graceful restart) is a feature to avoid traffic interruption when a cluster is restarted or reloaded. There are several cases when the Opaque LSA will be sent to the OSPF neighbor(s), such as the following: The cluster is upgraded. The primary unit is rebooted with the command 'exec reboot'. A failover occurs due to the command 'diagnose sys ha reset-uptime'. A failover occurs due to a change in unit priority. The routing process is restarted by running the command 'execute router restart'. When the command 'execute router clear ospf process' is executed, the Opaque LSA will not be sent to the OSPF neighbor(s) even if the graceful restart is configured.  This is expected behavior as this command will not trigger a router restart but will instead trigger process restart, therefore not meeting the trigger condition. The command 'exec router clear ospf process' will cause an interruption and should be executed during a maintenance window.