H3C Technologies H3C SecPath F1000-E - Manual (Page 151)

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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 6to4 relay router.
As shown in
Figure 2 , a static route must be configured on the border router in the 6to4 network and the
next-hop address must be the 6to4 address of the 6to4 relay router. 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 between the 6to4 network (with the address prefix starting with 2002) and the IPv6 network
is realized.
Figure 2 Principle of 6to4 tunnel and 6to4 relay
5. 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-multipoint 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 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 3 Principle of ISATAP tunnel