H3C Technologies H3C SecPath F1000-E - Manual (Page 149)

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2. After determining according to the routing table that the packet needs to be forwarded through the
tunnel, the device at the source end of the tunnel encapsulates the IPv6 packet with an IPv4 header
and forwards it through the physical interface of the tunnel.
3. The encapsulated packet goes through the tunnel to reach the device at the destination end of the
tunnel. The device at the destination end de-encapsulates the packet if the destination address of
the encapsulated packet is the device itself.
4. The destination device forwards the packet according to the destination address in the
de-encapsulated IPv6 packet. If the destination address is the device itself, the device forwards the
IPv6 packet to the upper-layer protocol for processing.
Configured tunnel and automatic tunnel
An IPv6 over IPv4 tunnel can be established between hosts, between hosts and devices, and between
devices. The tunnel destination needs to forward packets if the tunnel destination is not the final
destination of the IPv6 packet.
Tunnels are divided into configured tunnels and automatic tunnels depending on how the IPv4 address
of the tunnel destination is acquired.
• If the destination address of an IPv6 over IPv4 tunnel cannot be acquired from the destination
address of IPv6 packets, it needs to be configured manually. Such a tunnel is called a configured
tunnel.
• If the interface address of an IPv6 over IPv4 tunnel has an IPv4 address embedded into an IPv6
address, the IPv4 address of the tunnel destination can be acquired automatically. Such a tunnel is
called an automatic tunnel.
Type
According to the way an IPv6 packet is encapsulated, IPv6 over IPv4 tunnels are divided into the
following types:
Tunnel type Tunnel mode
IPv6 manual tunnel
Manually configured tunnel
IPv6-over-IPv4 GRE tunnel (GRE tunnel for short)
Automatic IPv4-compatible IPv6 tunnel
6to4 tunnel Automatic tunnel
Intra-site automatic tunnel addressing protocol (ISATAP) tunnel
The configuration parameters for each tunnel mode are listed in the following table:
Tunnel mode Source/destination IP address of the tunnel
IP address of the tunnel
interface
IPv6 manual
tunnel The source/destination IP address is a manually
configured IPv4 address.
IPv6 address
IPv6-over-IPv4
GRE tunnel The source/destination IP address is a manually
configured IPv4 address.
IPv6 address
Automatic
IPv4-compatible
IPv6 tunnel
The source IP address is a manually configured IPv4
address, while the destination IP address does not
need to be configured.
IPv4-compatible IPv6 address, in
the format
of ::IPv4-source-address/96