3Com S7906E Configuration Manual page 498

Tunnel type
Manually configured tunnel
Automatic tunnel
The configuration parameters for each tunnel mode are listed in the following table:
Tunnel mode Source/destination IP address of the tunnel
IPv6 manual The source/destination IP address is a manually
tunnel configured IPv4 address.
The source IP address is a manually configured
6to4 tunnel IPv4 address, while the destination IP address
does not need to be configured.
The source IP address is a manually configured
ISATAP tunnel IPv4 address, while the destination IP address
does not need to be configured.
1) IPv6 manually configured tunnel
A manually configured tunnel is a point-to-point link. Each link is a separate tunnel. IPv6 manually
configured tunnels are mainly used to provide stable connections for regular secure communication
between border routers or between border routers and hosts for access to remote IPv6 networks.
2) 6to4 tunnel
An automatic 6to4 tunnel is a point-to-multipoint tunnel and is used to connect multiple isolated IPv6
networks over an IPv4 network to remote IPv6 networks. The embedded IPv4 address in an IPv6
address is used to automatically acquire the destination IPv4 address of the tunnel.
The automatic 6to4 tunnel adopts 6to4 addresses. The address format is 2002:abcd:efgh:subnet
number::interface ID/64, where 2002 represents the fixed IPv6 address prefix, and abcd:efgh
represents the 32-bit globally unique source IPv4 address of the 6to4 tunnel, in hexadecimal notation.
For example, 1.1.1.1 can be represented by 0101:0101. The part that follows 2002:abcd:efgh uniquely
identifies a host in a 6to4 network. The tunnel destination is automatically determined by the embedded
IPv4 address, which makes it easy to create a 6to4 tunnel.
Because the 16-bit subnet number of the 64-bit address prefix in 6to4 addresses can be customized
and the first 48 bits in the address prefix are fixed to a permanent value and the IPv4 address of the
tunnel source or destination, it is possible that IPv6 packets can be forwarded by the tunnel.
3) ISATAP tunnel
With the application of the IPv6 technology, there will be more and more IPv6 hosts in the existing IPv4
network. The ISATAP tunneling technology provides a satisfactory solution for IPv6 application. An
ISATAP tunnel is a point-to-point automatic tunnel. The destination of a tunnel can automatically be
acquired from the embedded IPv4 address in the destination address of an IPv6 packet.
When an ISATAP tunnel is used, the destination address of an IPv6 packet and the IPv6 address of a
tunnel interface both adopt special ISATAP addresses. The ISATAP address format is
prefix(64bit):0:5EFE:ip-address. The 64-bit prefix is the prefix of a valid IPv6 unicast address, while
IPv6 manual tunnel
6to4 tunnel
Intra-site automatic tunnel addressing protocol (ISATAP) tunnel
1-4
Tunnel mode
IP address of the tunnel
interface
IPv6 address
6to4 address, in the format of
2002:IPv4-source-address::/
48
ISATAP address, in the
format of
Prefix:0:5EFE:IPv4-source-a
ddress/64