ZXR10 5900E Series Configuration Guide (IPv6)
configured, the tunnel is called a configured tunnel, such as a 6in4 tunnel or a GRE
tunnel.
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If the interface address of the IPv6 over IPv4 tunnel assumes a special
IPv4-embedded IPv6 address format (i.e. the IPv4 address of the tunnel termination
point can be automatically obtained from the destination address of the IPv6 packet),
the tunnel is called an automatic tunnel, such as a 6to4 tunnel or an ISATAP tunnel.
There is another type of IPv4 or IPv6 over IPv6 tunnel (see RFC 2473). The protocol
encapsulates an IPv4 or IPv6 data packet so that the encapsulated data packet can be
transmitted in another IPv6 network. The data packet after the encapsulation is an IPv6
tunnel packet, as shown in
.
Figure 3-2 Principles of the IPv4 (or IPv6) over IPv4 Tunnel
In the above figure, Original data refers to the IPv4 or IPv6 packet.
IPv6 Tunnel Principle
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6in4 Tunnel
shows the operating principles of a 6in4 tunnel.
Figure 3-3 Principles of a 6in4 Tunnel
The 6in4 tunnel involves a tunnel encapsulation and decapsulation process.
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Encapsulation: If the packet egress interface is a tunnel interface when an IPv6
host or router or switch sends an IPv6 flow, the host or router first determines
the tunnel type. If the tunnel is a 6in4 tunnel, the host or router implements IPv4
3-2
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