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JasonX
JasonX
Explorer
March 21, 2025
Solved

Fortigate dropping contact with Fiber ONT

  • March 21, 2025
  • 1 reply
  • 727 views

It cuts in and out several times a day, sometimes dropping in strength and sometimes just cutting out. The ISP suggested connecting to the supplied Eero router to test it and since then it has been stable. The WAN on my 60F is set to DHCP and automatically sets itself when connected.  The set up worked seamlessly with the ONT directly connected to my WAN port on the gate for 5 or 6 months since installation.

Edit: Should not have tagged this Fortiwan as it that is a product.....don't know how to remove

Best answer by Atul_S

Hi Jason,

 

There could be multiple factors to validate before coming to any conclusion as to whether ONT  itself is malfunctioning or the ISP.Check if you can see an arp on the wan port when the issue occurs and try to sniff the ONT mac add in Fortigate by following the guide https://community.fortinet.com/t5/FortiGate/Technical-Tip-How-to-sniff-packets-by-MAC-Address-on-FortiGate/ta-p/197682

 

Have you ruled out the layer 1 issue by any chance? If not, try to change the cable or connect a PC directly behind ONT and see if the PC gets the IP add or not.

 

Thanks

1 reply

Atul_S
Staff & Editor
Atul_SAnswer
Staff & Editor
March 23, 2025

Hi Jason,

 

There could be multiple factors to validate before coming to any conclusion as to whether ONT  itself is malfunctioning or the ISP.Check if you can see an arp on the wan port when the issue occurs and try to sniff the ONT mac add in Fortigate by following the guide https://community.fortinet.com/t5/FortiGate/Technical-Tip-How-to-sniff-packets-by-MAC-Address-on-FortiGate/ta-p/197682

 

Have you ruled out the layer 1 issue by any chance? If not, try to change the cable or connect a PC directly behind ONT and see if the PC gets the IP add or not.

 

Thanks

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