Since April of this year after we moved our IT services to another area I faced with the problem - our Fortigate 100F cannot get an IP from ISP's DHCP, it usually happening when my ISP's device suddenly lose power on their side or we have the power failure from our side. It cannot obtain an IP until I plug the cable from the PON to the other router or PC directly, after that router or PC can get an IP and then I re-plug the cable back to Fortigate - it immediately get and IP too. And it's working until we are facing with the next power failure from ISP side again (from our side we decided such problem with the UPS and generator set).
This summer I opened ticket in the support, we communicated a long time, did a lot of tests (debug and packet capture sniffing) but there was no any result. From the ISP - they simply suggested us to use another router, for example Mikrotik which doesn't have such a problem.
Does anybody faced with the same problem? I tried to search in the Internet and found couple of topics with similar problem but they ended with no solution (2016-2017 year).
My Fortigate is up-to-dated to 7.2.3 build 1262. Now the WAN interface stuck on the "Connecting..." phase which will end with "Failed." I tried to re-enable interface, re-plug it physically, but only plugging it to the other router and back to Fortigate can help me now.
I have just opened new ticket, they now suggest me to try any other DHCP with my WAN port, I know what will they say finally, that WAN interface is working with the other server (before it worked without any problem with my local ISP) and then they will close the ticket... But it'll not help me at all. The ISP is also have an argument that the other router is working fine. So I am cornered now. Please help!!!