Internet Drops — FortiGate 40F Not Sending Packets to ISP

[vpatel]

Hi,

I’m experiencing an intermittent internet drop issue with my FortiGate 40F.

Here’s the situation:
- The ISP says they are not receiving any packets from my firewall when the issue occurs.
- The WAN port shows link/ACT lights ON and stable.
- When I connect my laptop directly to the upstream MikroTik RB3011UiAS-RM switch, I get internet without drops, so the ISP link and MikroTik appear to be fine.
- The FortiGate is connected to the MikroTik RB3011UiAS-RM, which does NAT/routing.
- This happens about once a day or every other day. It usually starts working again within 5–10 minutes, but today it did not recover on its own  I had to restart the firewall for it to work again.

I appreciate any guidance you can provide.

Thank you.

[toshi-esumi]

First thing I would check is the log. If any events in the log when it happened.
Then, you need to troubleshoot while it's down.
- check with sniffer if it's really not sending any packets from the wan port.
- if confirmed really not sending, run "flow debug" to see what happens to the packets from one of internal device toward the internet.
https://docs.fortinet.com/document/fortigate/7.6.3/administration-guide/54688/debugging-the-packet-f...

Toshi