Linux IP Tunnel Mini-Mini HOWTO

Why?

Mobile IP

IP Tunnels are required for many Mobile IP schemes.

VPN- Virtual Private Network

IP tunnels offer an intersting, cost-effective alternative to WAN's (Wide Area Networks). WAN's are typically created when there is a need to share network data between several geographical locations. WAN's are usually very expensive to implement: they require long-distance, high-speed data connections.

Although the internet now provides access to virtually anywhere on the planet, there are issues surrounding security and/or protocols. IP tunnelling can provide a solution for these issues. Some protocols, such as Novell IPX, are not native to the internet. Tunnels of IPX over IP can provide a means of linking separate IPX sites over the internet.

Another issue arises when one site wishes to share private data, such s NFS mounts, CVS repository servers, private web servers, or network backup with another site. Normally, each site is behind a firewall that prevents external access to the private data, thus preventing sharing. Tunnels that send encrypted IP over IP provide a means of connecting two local LANS, allowing them to share data, but keeping them behind the firewalls.

Technology

IPX Tunnels

Refere to the Linux IPX-HOWTO for additinal detail on setting up an IPX tunnel.

Mobile IP

There are a number of web sites covering Mobile IP issues.
http://anchor.cs.binghamton.edu/~mobileip/LJ/index.html

SKIP

Simple Key-Management for IP. Uses Diffie-Helmen to provide a simple, fast encrypted IP tunnel communications and key-management protocol. See SKIP, and the Linux implementation of SKIP, ENSKIP. The ENSKIP kernel module and encryption daemon build on top of the Linux firewall/masquerade technology to provide a WAN bridge between LAN segments.

SKIP for FreeBSD

Point-To-Point Tunnel

Build a VPN using ssh-pppd as a tunnel. See the VPN mini-HOWTO

IPIP

The Linux 2.0 and 2.1 series kernels provide support fot IP tunnels: /dev/tunl0, /dev/tunl1, etc.

IPSEC

VPN's can also be built by combining firewalls with IPSEC.

Install and Setup

1. Obtain and install a Linux v.2.0 or v.2.1 kernel
2. Configure the kernel for IP tunneling. Recompile. Reboot. If the kernel has been successfuly configured, then a 'cat /proc/net/dev' should show a tunl0 and tunl1 device, in additional to the usual lo and eth0 or ppp0
3. read /usr/src/linux/drivers/net/README.tunnel