Yesterday it worked.
Today it is not working.
Windows is like that.

So are networks, oddly enough.

There are many many ways you can set up a tunnel between two networked hosts. The MetaNet is one such example of a tunnel - it is a multi-point tunnel.

Most tunnels are point-to-point. Some examples are:

  • SSH Tunnels. Very easy to set up in user space. See SSHNotes for information.
  • IPSec - The 'secure' way to set up tunnels. Kinda broken under Linux atm.
  • L2TP - Layer 2 Tunnelling Protocol
  • GRE - Generic Routing Encapsulation. See GRETunnel for information
  • PPTP - Point To Point Tunnel Protocol
  • IPIP - IP over IP Tunnel

You may want to authenticate your users against another machine; look at RADIUS and TACACS.