H3C Technologies H3C S12500-X Series Switches - Manual (Page 147)

136
hexadecimal notation. For example, 1.1.1.1 can be represented by 0101:0101. The IPv4
address identifies a 6to4 network (an IPv6 network where all hosts use 6to4 addresses). The
border router of a 6to4 network must have the IPv4 address abcd:efgh configured on the interface
connected to the IPv4 network. The subnet number identifies a subnet in the 6to4 network. The
subnet number::interface ID uniquely identifies a host in the 6to4 network.
6to4 tunneling uses an IPv4 address to identify a 6to4 network. This method overcomes the
limitations of automatic IPv4-compatible IPv6 tunneling.
Figure 50 Principle of 6to4 tunneling
• ISATAP tunneling—An ISATAP tunnel is a point-to-multipoint automatic tunnel. It provides a solution
to connect an IPv6 host to an IPv6 network over an IPv4 network.
The destination addresses of IPv6 packets are all ISATAP addresses. The ISATAP address format is
prefix:0:5EFE:abcd:efgh. The 64-bit prefix is a valid IPv6 unicast address prefix. The
abcd:efgh/64 segments represent a 32-bit IPv4 address, which identifies the tunnel destination
but does not require global uniqueness.
ISATAP tunnels are mainly used for communication between IPv6 routers or between an IPv6 host
and an IPv6 router over an IPv4 network.
Figure 51 Principle of ISATAP tunneling
IPv4 over IPv4 tunneling
IPv4 over IPv4 tunneling (RFC 1853) enables isolated IPv4 networks to communicate. For example, an
IPv4 over IPv4 tunnel can connect isolated private IPv4 networks over a public IPv4 network.