H3C Technologies H3C S12500-X Series Switches - Manual (Page 146)

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physical interface of the tunnel. In the IPv4 header, the source IPv4 address is the IPv4 address of
the tunnel source, and the destination IPv4 address is the IPv4 address of the tunnel destination.
3. Upon receiving the packet, Device B de-encapsulates the packet.
4. If the destination address of the IPv6 packet is itself, Device B forwards it to the upper-layer
protocol. If not, Device B forwards it according to the routing table.
Tunnel modes
IPv6 over IPv4 tunnels include manually configured tunnels and automatic tunnels, depending on how
the IPv4 address of the tunnel destination is acquired.
• Manually configured tunnel—The destination IPv4 address of the tunnel cannot be automatically
acquired from the destination IPv6 address of an IPv6 packet at the tunnel source, and must be
manually configured.
• Automatic tunnel—The destination IPv4 address of the tunnel can be automatically acquired from
the destination IPv6 address (with an IPv4 address embedded) of an IPv6 packet at the tunnel
source.
According to the way an IPv6 packet is encapsulated, IPv6 over IPv4 tunnels are divided into the
following modes.
Table 9 IPv6 over IPv4 tunnel modes and key parameters
Tunnel type Tunnel mode
Tunnel source/destination
address
Destination IPv6 address
format
Manually
configured tunnel IPv6 over IPv4
manual tunneling
The source and destination IPv4
addresses are manually
configured.
Ordinary IPv6 address
Automatic tunnel
6to4 tunneling
The source IPv4 address is
manually configured. The
destination IPv4 address is
automatically obtained.
6to4 address, in the format of
2002:IPv4-destination-address::/
48, where the
IPv4-destination-address is the
IPv4 address of the tunnel
destination.
ISATAP tunneling
The source IPv4 address is
manually configured. The
destination IPv4 address is
automatically obtained.
ISATAP address, in the format of
Prefix:0:5EFE:IPv4-destination-ad
dress/64 where the
IPv4-destination-address is the
IPv4 address of the tunnel
destination.
• IPv6 over IPv4 manual tunneling—A point-to-point link and its source and destination IPv4
addresses are manually configured. You can establish an IPv6 over IPv4 manual tunnel to connect
isolated IPv6 networks over an IPv4 network, or connect an IPv6 network to an IPv4/IPv6 dual-stack
host over an IPv4 network.
• 6to4 tunneling—A point-to-multipoint automatic tunnel. It is used to connect multiple isolated IPv6
networks over an IPv4 network. The destination IPv4 address of a 6to4 tunnel is embedded in the
destination 6to4 address of packets. This mechanism enables the device to automatically get the
tunnel destination address, simplifying tunnel establishment.
The 6to4 address format is 2002:abcd:efgh:subnet number::interface ID/48, where 2002 is the
fixed IPv6 address prefix, and abcd:efgh represents a 32-bit globally unique IPv4 address in