Description
Changes in network infrastructure will sometimes reflect in the logs, in this example we observe ICMP type 1 error code 5 (no protocol tuple found, drop) which means that the Fortigate cannot find a route to the destination.
Scope
ICMP error codes
Solution
To correct the issue please see ICMP error code table. If for a example a subnet has been decommissioned, routes and policies to that destination may have to be modified or removed from the Fortigate's configuration.
