IP Tunneling

IP Tunneling
An Introduction

Prof. David Bernstein
James Madison University

Computer Science Department

bernstdh@jmu.edu

Overview

What Is It?
- Embedding one IP packet in another IP packet
Why Bother?
- Create a virtual link between two routers
- Virtual Private Networking (VPN)
- Running IPv6 over IPv4
Does This Break IP?
- To the rest of the network, the tunneled packet looks like a regular IP packet

The Process

Normal IP Forwarding:
- A creates a packet destined for B
- Router R forwards the packet to router S
- Router S delivers the packet to B
Tunneling:
- A creates a packet destined for B
- Router W embeds that packet in one destined for Z
- Router Z strips the outer packet and delivers the inner packet to B