Skip to main content
G
GEHCS
Visitor III
June 24, 2026
Question

FortiOS on Fortigate: diagnose debug application {netlink|linkd}

  • June 24, 2026
  • 4 replies
  • 91 views

In what FortiOS version did this last work? The AI chatbots of the day insist it should still work, but the CLI is a mess.

I need to monitor in real time interface OSI layer1 state change (simplest of requests)

What is the best replacement in in version 7.2, 7.4, 7.6?

 

diagnose debug console timestamp enable
!
diagnose debug disable
diagnose debug reset
!
diagnose debug application linkd -1  
diagnose debug application netlink -1
!
diagnose debug duration 0
diagnose debug enable
!

 

    4 replies

    BSeklecki_GEVernova
    BSeklecki_GEVernova
    Explorer II
    June 24, 2026

    Things aren’t looking so go in v7.6.  fnsysctl tail -F doesn’t work either:


    FortiGate-121G #  fnsysctl tail -F /var/log/messages
    can not find command tail
     

      sjoshi
      Staff
      sjoshi
      Staff
      June 25, 2026

      To monitor layer1 status refer below article:

      https://community.fortinet.com/fortigate-3/technical-tip-layer-1-and-layer-2-troubleshooting-with-2-simple-commands-199689

      Thanks, Salon
        Toshi_Esumi
        SuperUser
        Toshi_Esumi
        SuperUser
        June 25, 2026

        None of these would give the time stamp when L1 status changes. I guess only log events would be the closest alternative.

        Toshi 

          BSeklecki_GEVernova
          BSeklecki_GEVernova
          Explorer II
          June 25, 2026

          Yea but how to tail the system event logs? It seems that was removed in recent editions when: “fnsysctl tail -F” was disabled?

          FortiNet even removed:

          diagnose debug application eventlog -1
            BSeklecki_GEVernova
            BSeklecki_GEVernova
            Explorer II
            June 25, 2026

            I’m just trying to imagine a millennial or gen-z newly hired engineer at Cisco sitting in their first  staff meeting, then standing to pitch a proposal to senior product engineers:

            “Hey guys, after 30 years, lets remove “logging console informational / terminal monitor” commands from the next release of IOS-XE”.   

            Their LDAP account would be deleted before they sat back down in their seat.

            BSeklecki_GEVernova
            BSeklecki_GEVernova
            Explorer II
            June 25, 2026

            The “system event log” has most (*) of the useful information one needs.  If only there was some way….using a POSIX like tool…..to “tail” that file.  Hmm…

            (*) Cisco %LINEPROTO-5-UPDOWN% messages print OSI Layer1 details (Speed, etc.)

              Terms & ConditionsAccessibility statement