NTS TunnelBuilder was a PPTP/L2TP VPN client for System 7.1 and up.
The downloadable file is the evaluation version from the NTS website.
Compatibility
Architecture: 68k PPC
? Mac OS-compatible computer with 68030 processor or later
? Mac OS version 7.1 or later (version 7.5 or later recommended)
? Open Transport 1.0.8 or later (1.1.2 or later recommended)
? 8 megabytes (MB) of RAM (16 MB recommended)
? 6 MB of available hard disk space