Operation Manual – IPv6
H3C S3610&S5510 Series Ethernet Switches
Chapter 3 Tunneling Configuration
3-3
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If the IPv4 address is embedded into the IPv6 address, the IPv4 address of the
tunnel destination can automatically be acquired from the destination address of
the IPv6 packet. Such a tunnel is called an automatic tunnel.
III. Type
According to the way an IPv6 packet is encapsulated, IPv6 over IPv4 tunnels are
divided into the following types:
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IPv6 manual tunnel
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Automatic IPv4-compatible IPv6 tunnel
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6to4 tunnel
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ISATAP tunnel
Among the above tunnels, the IPv6 manual tunnel is a configured tunnel, while the
automatic IPv4-compatible IPv6 tunnel, the 6to4 tunnel, and intra-site automatic tunnel
address protocol (ISATAP) tunnel are automatic tunnels.
1)
IPv6 manually configured tunnel
A manually configured tunnel is a point-to-point link. One link is a separate tunnel. The
IPv6 manually configured tunnels provide stable connections requiring regular secure
communication between two border routers or between a border router and a host for
access to remote IPv6 networks.
2)
Automatic IPv4-compatible IPv6 tunnel
An automatic IPv4-compatible IPv6 tunnel is a point-to-multipoint link. IPv4-compatible
IPv6 addresses are adopted at both ends of such a tunnel. The address format is
0:0:0:0:0:0:a.b.c.d/96, where a.b.c.d represents an embedded IPv4 address. The
tunnel destination is automatically determined by the embedded IPv4 address, which
makes it easy to create a tunnel for IPv6 over IPv4. However, because an automatic
IPv4-compatible IPv6 tunnel must use IPv4-compatible IPv6 addresses and it is still
dependent on IPv4 addresses. Therefore, automatic IPv4-compatible IPv6 tunnels
have limitations.
3) 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 of the
tunnel. The automatic 6to4 tunnel adopts 6to4 addresses. The address format is
2002:abcd:efgh:subnet number::interface ID/64, where abcd:efgh represents the 32-bit
source IPv4 address of the 6to4 tunnel, in hexadecimal notation. For example, 1.1.1.1
can be represented by 0101:0101. The tunnel destination is automatically determined
by the embedded IPv4 address, which makes it easy to create a 6to4 tunnel.
Since 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 by a permanent value
and the IPv4 address of the tunnel source or destination, it is possible that IPv6 packets