IPv6 Tunneling over IPv4 Networks: Important Facts and Considerations

IPv6 Tunneling: Key Points

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Question

Which three statements are true about tunneling IPv6 traffic over IPv4 networks? (Choose three.)

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Explanations

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A. B. C. D. E.

ADE

Tunneling requires encapsulation of the IPv6 packet within an IPv4 header. The new IPv4 packet is then forwarded across the IPv4 network to the other end of the tunnel, where the IPv4 header is removed and the IPv6 packet is either processed or forwarded.

Tunneling IPv6 traffic over IPv4 networks involves encapsulating IPv6 packets inside IPv4 packets, which enables IPv6 packets to be transported over an IPv4 infrastructure. The following are the three true statements about this process:

A. The source tunnel endpoint encapsulates the native IPv6 packet inside IPv4: When a device at the edge of an IPv6 network sends a packet to a destination that is only reachable over an IPv4 network, it needs to encapsulate the IPv6 packet inside an IPv4 packet. The source tunnel endpoint is responsible for this encapsulation process. This encapsulated packet is then routed through the IPv4 infrastructure until it reaches the destination tunnel endpoint.

C. The intermediary hops are responsible for de-encapsulating and re-encapsulating the IPv4 packet to process the IPv6 payload: When an encapsulated packet travels through the IPv4 infrastructure, the intermediary hops that forward the packet are responsible for de-encapsulating the IPv4 packet to extract the original IPv6 payload. After extracting the payload, the intermediary hops will re-encapsulate the packet with a new IPv4 header and forward it to the next hop. This process continues until the packet reaches the destination tunnel endpoint.

E. The destination tunnel endpoint de-encapsulates the IPv6 packet and forwards/processes the packet natively: When the encapsulated packet reaches the destination tunnel endpoint, the endpoint is responsible for de-encapsulating the packet to extract the original IPv6 payload. After extracting the payload, the destination tunnel endpoint can process the packet natively as an IPv6 packet.

Statements B and D are false:

B. The source tunnel endpoint disassembles the IPv6 packet and reassembles it as IPv4: This statement is incorrect because the source tunnel endpoint does not disassemble the IPv6 packet. Instead, it encapsulates the IPv6 packet inside an IPv4 packet.

D. The source tunnel endpoint forwards the IPv4 network with the encapsulated IPv6 payload through the IPv4 network: This statement is incorrect because the source tunnel endpoint does not forward the IPv4 network with the encapsulated IPv6 payload. Instead, it forwards an encapsulated packet that contains an IPv6 payload inside an IPv4 header. The packet is then de-encapsulated and re-encapsulated by the intermediary hops as it travels through the IPv4 network.