Troubleshooting
The following diagnose commands are available for further IS-IS troubleshooting and will display all IS-IS activity (sent and received packets):
FGT # diagnose ip router isis level info
FGT # diagnose ip router isis all enable
FGT # diagnose debug enable
...to stop the debug type output :
FGT # diagnose ip router isis level none
Output and interpretation depends on the issue faced. You can provide this information to TAC if you open a support ticket.