H3C S9500 Series Operation Manual page 135

Operation Manual – Tunneling
H3C S9500 Series Routing Switches
A manually configured tunnel is a point-to-point link. One link is a separate tunnel. The
IPv6 manually configured tunnel is mainly used for stable connections requiring regular
secure communication between two border routers or between a border router and a
host, or for connections 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, 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 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. A 6to4 tunnel interconnects IPv6 networks over an IPv4
network, and overcomes the limitations of an automatic IPv4-compatible IPv6 tunnel.
4) 6to4 relay
A 6to4 tunnel is only used to connect 6to4 networks, whose IP prefix must be 2002::/16.
However, IPv6 network addresses with a prefix such as 2001::/16 may also be used in
IPv6 networks. To connect a 6to4 network to an IPv6 network, a 6to4 router must be
used as a gateway to forward packets to the IPv6 network. Such a router is called a
6to4 relay router.
As shown in
A) in the 6to4 network and the next-hop address must be the 6to4 address of the 6to4
relay router (Router C). In this way, all packets destined for the IPv6 network will be
forwarded to the 6to4 relay router, and then to the IPv6 network. Thus, interworking
Figure 1-2, a static route must be configured on the border router (Router
Chapter 1 Tunneling Configuration
1-4