HP VPN Firewall Appliances VPN Configuration Guide

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Figure 56 IPv6 over IPv4 tunnel
The IPv6 over IPv4 tunnel processes packets as follows:
1. A host in the IPv6 network sends an IPv6 packet to Device A at the tunnel source.
2. After determining according to the routing table that the packet needs to be forwarded through the
tunnel, Device A 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.
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 for processing. If not, Device B forwards it according to the routing table.
NOTE:
During the de-encapsulation process, if the IPv4 address in an IPv4 header is a private address, the device
does not discard the packet.
Tunnel types
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 4 IPv6 over IPv4 tunnel modes and key parameters
Tunnel type Tunnel mode
Tunnel source/destination
address
Tunnel interface
address t
yp
e
Manually
configured tunnel
IPv6 manual tunneling
The source and destination IPv4
addresses are manually
configured.
IPv6 address