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Consider the case where there are 2 computers using the IPV6 protocol that want to communicate with each other, and the packet(s) must pass through a network that uses the IPV4 protocol. Can the packet(s) travel through that network? How?

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    This isn't a real question. It's an invitation to write an essay to demonstrate knowledge. That's why it uses the word "justify". Mar 21, 2014 at 21:13

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IPv6 packets can only travel over an IPv6 network. If a region of the network only supports IPv4 then the IPv6 packets cannot natively cross it. To make this work you need to simulate an IPv6 connection over the IPv4 network. That is called a tunnel. Two routers that have both IPv4 and IPv6 can tunnel traffic between them by putting the IPv6 packets inside IPv4 packets and sending them to each other over IPv4. That way it looks like there is a direct IPv6 connection between those routers and in such a way you can create a full IPv6 path end-to-end:

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Technologies often used to build such a tunnel are 6in4 and GRE.

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    The term used for "simulating" an IPv6 over IPv4 is "encapsulation".
    – LawrenceC
    Mar 22, 2014 at 13:25
  • The terms 'encapsulation' and 'tunnelling' are very tricky. The term 'encapsulation' means 'putting one packet inside another packet'. A tunnel is usually understood to consist of a fixed set of endpoints that encapsulate traffic between them, thereby creating a virtual link. It gets tricky when the number of endpoints is larger than 2 (multipoint), dynamic (LISP routing protocol) or even undefined (like 6to4 where every public IPv4 address is a potential endpoint). Defining 'the tunnel' becomes difficult then, so just talking about encapsulation is then easier :) Mar 22, 2014 at 16:39
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No. You should use tunelling in this case. Like Teredo or 6to4.

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    Teredo and 6to4 should never be encouraged. They cause too much unreliability. Manual tunnels like 6in4 or GRE are ok, but should only be used when native IPv6 isn't available. Mar 21, 2014 at 7:24

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