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Networking Fundamentals · Intermediate

Tunneling

Encapsulating one protocol's packets inside another protocol so they can cross a network that does not support them natively.

Definition

IPv6-over-IPv4 tunnels carry IPv6 across IPv4-only networks, VPN tunnels carry private traffic across the Internet, and GRE carries arbitrary Layer 3 traffic. Tunnels add header overhead, reducing the effective MTU.

Example

A 6in4 tunnel uses IP protocol 41 to carry IPv6 packets inside IPv4.

Exam tip

IPv6-in-IPv4 tunneling uses IP protocol 41.

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