Technical Tip: Unable to access local LAN resources when connected to IPsec dial-up Full Tunnel

In this example, an IPsec Dial Up Full tunnel (DHCP over IPsec) is configured.

The local PC <10.190.3.113> can ping other local resources inside the same subnet. In this instance, the gateway <10.190.1.193> is reachable.

 
The traffic is being routed through the tunnel instead. 

To resolve this without enabling split-tunneling, select 'Enable Local LAN' under the FortiClient Phase1.

Once enabled, the local resources should be reachable now while connected to the IPsec VPN.

Additional Scenario: Windows clients are unable to access internal resources.

Another scenario may occur where both macOS and Windows users can successfully connect using FortiClient, but only the Windows clients are unable to access or ping internal network resources.

If this happens, try disabling, saving, and then re-enabling NAT Traversal in both. The Dial-Up VPN configuration on the FortiGate and within the FortiClient application.


This issue has been observed with FortiClient v7.4.1, v7.4.2, and v7.4.3.

Notes:

• This applies only to Windows clients. NAT Traversal is not available as a configurable option in FortiClient for macOS.
• The public IP address of the FortiGate, which is used as the remote gateway, also becomes unreachable once the dial-up client connects to the VPN. However, enabling 'Enable Local LAN' in FortiClient allows the client to reach it.

Related articles:
Technical Tip: FortiGate IPSec VPN resource list
Technical Tip: IPsec dial-up full tunnel with FortiClient