FortiClient Enterprise Linux IPsec disconnects exactly ~9 seconds after successful connection (RHEL 9 / Ubuntu 24.04)

Hi everyone,

We are troubleshooting what appears to be a Linux-specific FortiClient Enterprise issue and I would like to know if anyone has experienced something similar.

Environment:

• FortiClient Enterprise Linux 7.4.7 build 5438
• FortiGate 7.4.x
• IPsec VPN (IKEv2)
• RHEL 9.x and Ubuntu 24.04

Behaviour:

• VPN authentication succeeds.
• Tunnel is established successfully.
• Approximately 9 seconds later the VPN disconnects.
• The timing is very consistent (always around 9 seconds).

What we have already verified:

• Same FortiGate configuration works perfectly with FortiClient Enterprise for Windows.
• Reproduced on both RHEL 9 and Ubuntu 24.04.
• Reproduced on both physical and virtual machines.
• Reproduced on x86_64 (and also ARM64 with 7.4.7 where supported).
• Client is not registered to EMS.
• FortiGate logs do not show authentication failures, DPD timeout, IKE negotiation errors or peer-initiated disconnects.
• The Linux client appears to terminate the session locally after the tunnel has already been established.

We are currently testing older Linux releases (7.4.6 / 7.4.5 where available) to determine whether this is a regression.

Has anyone experienced a deterministic disconnect after about 9 seconds on Linux?

Any information, workaround, or TAC feedback would be greatly appreciated.