H3C Technologies H3C S5560 Series Switches - Manual (Page 222)

207
The outgoing interface is the tunnel interface, so Device A knows that the packet needs to be
forwarded through the tunnel.
b. Encapsulates the IPv6 packet with an IPv4 header and forwards it through the 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.
2. Upon receiving the packet, Device B de-encapsulates the packet.
3. 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. It 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 10 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.