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Switch blocking uplink to FG80F after 6.4.9 update

Last night I updated my Fortigate 80F from 6.4.8 to 6.4.9 and immediately lost connection to the LAN. I could still ping the Fortigate from the internet side, so on a hunch I checked the switch (a Unifi 24PoE) and noticed the port the 80F is plugged into was blocked. Disabling STP on the port makes everything work again. I'm not sure if it's a Ubiquiti problem or a Fortigate problem, but it had been running fine on 6.4.8 for months. There's only one connection between the 80F and the switch. RSTP priority on the switches is set to 4096 on the 24PoE and 8192 on a couple of downstream switches. I skimmed the release notes for 6.4.9 and nothing stood out that might cause this kind of issue...any ideas?

New Contributor

Any update about this issue? i have exactly the same problem... The same version 6.4.9 on others equipments.


The issue has been resolved in FortiOS 6.4.10.

It's mentioned in the "Resolved issues" section of FortiOS 6.4.10 release notes.

809366 - FG-40F with STP enabled on a hardware switch creates a loop after upgrading to 6.4.9.


Hello meliodes,


I think are  hitting bug No 0809366 which is fixed on 6.4.10.


New Contributor

I am not sure if this is related but I seem to be having this issue in 7.0.11. I am using a FWF-40F. It only happens when using a software switch. When I use a physical interface there is no problem. When I do a tcpdump on the interface that is associated with the software switch I see a bunch of STP packets coming out of the FortiNet device.

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