Internet connection lost when trying to connect to a Fortigate with IPsec VPN through Forticlient

Forum|Forum|10 months ago
September 17, 2025
13 replies
1425 views

Hello guys,

not sure if someone else has the same issue, but there are times when I'm trying to set up a remote connection tunnel via IPsec and this issue comes up... I'm trying to connect through Forticlient VPN but internet connection stops, the tunnel is (of course) down and the internet access is restored.

FortiGate

AEK

SuperUser

Hi Alejandro

Can you share your routing table when IPsec connection is down and when it is up?

AEK

Alejandro77Author

New Member

that was my first thought too and I checked it.. it was identical! Perhaps I'll need to rephrase: While trying to connect, internet dropped, so the connection never happened. I checked the routing table both times and it was identical

AEK

SuperUser

Did you enter the remote server as fqdn or ip?

Also can you share the ipsec config? I mean from FGT side.

AEK

Debbie_FTNT

Staff & Editor

It does sound a bit like FortiClient/routing may be set up to send everything through the VPN tunnel (no split-tunnel), and if FortiGate lacks the policies to allow this, internet access would essentially be down after VPN is established.

AEK

SuperUser

that was my first thought too and I checked it.. it was identical! Perhaps I'll need to rephrase: While trying to connect, internet dropped, so the connection never happened. I checked the routing table both times and it was identical

In this case I suspect some incompatibility issue with the network driver. Can you using another network interface? I mean if you are using WiFi try with Ethernet, and vice versa.

AEK

Alejandro77Author

New Member

Finally the issue was ports 500 and 4500 that were closed by the ISP...
Thank you very much guys for the support!!!

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