Protocols And Standards - H3C LS-3100-52P-OVS-H3 Operation Manual

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
ip-address is a 32-bit source IPv4 address in the form of a.b.c.d or abcd:efgh, which need not be
globally unique. Through the embedded IPv4 address, an ISATAP tunnel can automatically be created
to transfer IPv6 packets.
The ISATAP tunnel is mainly used for connection between IPv6 routers or between a host and an IPv6
router over an IPv4 network.
Figure 1-2 Principle of ISATAP tunnel

Protocols and Standards

RFC 1853: IP in IP Tunneling
RFC 2473: Generic Packet Tunneling in IPv6 Specification
RFC 2893: Transition Mechanisms for IPv6 Hosts and Routers
RFC 3056: Connection of IPv6 Domains via IPv4 Clouds
RFC 4214: Intra-Site Automatic Tunnel Addressing Protocol (ISATAP)
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