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IP Tunneling
An Introduction


Prof. David Bernstein
James Madison University

Computer Science Department
bernstdh@jmu.edu

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Overview
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  • 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
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  • 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
There's Always More to Learn
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