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AlexFerenX
AlexFerenX
Visitor III
July 21, 2025
Question

Meaning and significance of "scope" in FIB printouts?

  • July 21, 2025
  • 1 reply
  • 1067 views

Hi!

every KB I've seen, including 212757 & 199661, omits explanation of "scope" attribute in Kernel Table/FIB printout.

I understand it originate from Linux Kernel Table, but, in Fortigate context, can anyone may volunteer qualified meanings of 0, 253, 254 and 255, and significance of each?

Thanks!

1 reply

esalija
Staff
esalija
Staff
July 21, 2025

Hi @AlexFerenX 

 

In the context of Kernel routing tables, the "scope" value indicates the reachability of a route.

- A "scope" value of 0 indicates a global route.

This means the route is valid for the entire network and can be used to route traffic beyond the local network segment.

- A "scope" value of 253 typically represents a site-local route.

- This means the route is intended for use within a specific site or organisation and is not meant to be used for routing traffic outside of that site.

- A scope value of 254 typically represents a link-local route.

This means the route is only valid within the local network segment and is not intended for routing traffic beyond the local link.

- A "scope" value of 255 typically represents a host route.

This means the route is specific to a single host or device, and it is used to direct traffic to that particular host.

Best regards,
Erlin

    AlexFerenX
    AlexFerenXAuthor
    Visitor III
    July 21, 2025

    Hi @esalija,

    thank you.

    So we're on same page - is yours a Linux-generic or is it FortiOS-specific answer? 

    I have to ask because "...  route is intended for use within a specific site or organisation ..." doesn't seem FortiOS-specific at all.

    Alex

    esalija
    Staff
    esalija
    Staff
    July 21, 2025

    HI @AlexFerenX 

     

    The explanation provided for scope values is more aligned with general networking concepts and Linux-based systems rather than being FortiOS-specific.

    Best regards,

    Erlin

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