strongSwan: strongSwan is another open-source IPSec VPN solution primarily designed for Linux, but it also has clients for Windows. It offers good documentation and can be a reliable choice for advanced users.

here are some Windows freeware IPsec client software that you can use to join a Sangfor NGAF IPsec VPN:

    Shrew Soft VPN Client is a free and open-source IPsec VPN client that is compatible with Sangfor NGAF IPsec VPNs.
    SoftEther VPN Client is another free and open-source IPsec VPN client that is compatible with Sangfor NGAF IPsec VPNs.
    IKEv2 VPN is a built-in IPsec VPN client in Windows 10 and Windows 11. To use IKEv2 VPN to connect to a Sangfor NGAF IPsec VPN, you will need to create a VPN connection profile in the Windows Settings app.

Here are some instructions on how to create a VPN connection profile in the Windows Settings app:

    Open the Windows Settings app.
    Click Network & Internet.
    Click VPN.
    Click Add a VPN connection.
    In the VPN provider drop-down list, select Windows (built-in).
    In the Connection name box, enter a name for your VPN connection.
    In the Server name or address box, enter the IP address or hostname of the Sangfor NGAF IPsec VPN server.
    In the VPN type drop-down list, select IKEv2/IPsec.
    Click Create.

Once you have created a VPN connection profile, you can connect to the Sangfor NGAF IPsec VPN by following these steps:

    Click the Start button and type VPN.
    Click the VPN app.
    Click the Connection name of the VPN connection you created in the previous steps.
    Click Connect.

IKEv2 VPN Clients (built-in): Windows operating systems, including Windows 7 and later, have built-in support for the IKEv2 VPN protocol. You can configure an IKEv2 VPN connection manually through the Windows settings. This is a native solution that doesn't require third-party software.

OpenConnect GUI: OpenConnect is an open-source VPN client that supports SSL VPNs. While it's not IPSec, it's widely used for connecting to various VPNs, including Cisco AnyConnect-compatible VPNs. The OpenConnect GUI is a user-friendly front-end for OpenConnect on Windows.

FortiClient: FortiClient is a free VPN client provided by Fortinet, a well-known network security and VPN solutions provider. While it's primarily designed for Fortinet's own products, it can connect to IPSec VPNs from other vendors as well.

FreeS/WAN: FreeS/WAN is another open-source IPSec implementation, originally developed for Linux but with some compatibility for Windows. It might require more technical expertise to set up and configure.

Yes, Sangfor did provide a VPN client for Windows called "Sangfor SSL VPN Client." However, for IPsec VPN connections, you might need third-party IPsec VPN client software because Sangfor primarily focused on SSL VPN. A commonly used IPsec VPN client for Windows is Shrew Soft VPN Client, which is free and open-source.

To configure the IPsec VPN server in Sangfor NGAF, the steps typically involve:

Access NGAF Console: Log in to the Sangfor NGAF web-based console.

Navigate to VPN Settings: Find the VPN settings or IPsec VPN configuration section within the NGAF console.

Create VPN Policy: Create an IPsec VPN policy, specifying details such as the encryption algorithm, authentication method, and IP ranges.

User Authentication: Configure user authentication, which may involve setting up user accounts or integrating with your existing user management system.

Peer Configuration: Define the IPsec peer settings, including the remote gateway's IP address or domain name.

Phase 1 and Phase 2 Configuration: Configure Phase 1 and Phase 2 parameters, such as encryption and authentication methods.

Security Policies: Define security policies for traffic allowed over the IPsec VPN connection.

Testing and Activation: Test the configuration by connecting a client using an IPsec VPN client like Shrew Soft.