Technical data

Away from home, the mobile node sends a home address option to inform the
receiver of its home address enabling the receiver to correctly identify the
connection to which the packet belongs. When the mobile node returns to its
homelink,themobilenodesendsabindingupdatetothehomeagentandtothe
correspondent node to clear the bindings.
For more information about mobile IPv6, refer to the TCP/IP Services release notes.
9.2 Understanding How Tunnels Work
Tunneling IPv6 packets in IPv4 is a mechanism that allows IPv6 nodes to
interoperate with IPv4 hosts and routers. This approach enables the gradual
deployment of IPv6 in your network.
OpenVMS systems can have both an IPv4 address and an IPv6 address. An end
system with both addresses is considered a v4/v6 host; a router with both addresses
is considered a v4/v6 router. A v4/v6 host can use IPv6 to communicate with other
v4/v6 hosts on the same communications link. However, when these hosts need
to communicate over an IPv4 network, the hosts need to tunnel the IPv6 packets
in IPv4 packets in order for the IPv4 routing infrastructure to route the packets
to the destination host.
The OpenVMS implementation of tunneling IPv6 packets in IPv4 uses bidirectional
configured tunnels to carry IPv6 packets through an IPv4 routing infrastructure;
unidirectional tunnels are not supported. This means that a configured tunnel
must be created on the nodes at both ends of the tunnel. A bidirectional
configured tunnel behaves as a virtual point-to-point link. For the remainder of
this chapter, the term configured tunnel refers to a bidirectional configured tunnel.
A configured tunnel has a source IPv4 address and a destination IPv4 address.
Table 9–1 describes which configured tunnels are possible.
Table 9–1: Tunnel Configurations
Tunnel
Configuration
Description Described in...
Router-to-router
tunnel
The v4/v6 routers are connected
by an IPv4 infrastructure. For
end-to-end communications, this
represents only one segment of
the total path.
Section 9.3.3
Host-to-router
tunnel
The v4/v6 host and v4/v6 router
are connected by an IPv4
infrastructure. For end-to-end
communications, this represents
the first segment of the total
path.
Section 9.3.1
Host-to-host
tunnel
The v4/v6 hosts are connected
by an IPv4 infrastructure. For
end-to-end comm
unications, this
represents the total path since
the tunnel spans the total path.
Router-to-host
tunnel
The v4/v6 router and v4/v6
host are connected by an IPv4
infrastructure. For end-to-end
communications, this represents
the final segment of the total
path.
Section 9.3.2
IPv6 9–3