HP-UX IPv6 Transport Administrator's Guide for TOUR 2.0 (April 2004, rev 2)

IPv6 Addressing and Concepts
Stateless Address Autoconfiguration
Chapter 664
Manual Configuration and Router Advertisements
Note that even if a primary interface is manually configured, if the host
receives prefixes from router advertisements, then secondary interfaces
are autoconfigured. In this case, the addresses on the secondary
interfaces are derived from the interface ID portion of the manually
specified primary interface address.
Manual Configuration Overwriting Autoconfiguration
Manual configuration can overwrite autoconfiguration. When a
secondary interface is configured with a manually assigned address, and
if the user chooses an interface index number that has been used for an
already autoconfigured secondary interface, the manual configuration
overwrites the autoconfiguration. When this happens, network
connectivity through the overwritten autoconfigured IP address is
temporarily lost. At a later time, when the host receives the next router
advertisement, the host will bring up another secondary interface with a
different IP index number, but with the same IP address, and network
connectivity through that IP address is restored. Normally, a user can
avoid this by checking used IP index numbers. However, there is always
a possibility that address autoconfiguration due to router advertisement
is happening concurrently while the user manually configures secondary
interfaces.
Disabling Specific IPv6 Interfaces
To disable communication through a specific IP address on an
autoconfigured secondary interface, that secondary interface must be
marked down, not removed or overwritten with a different IP address. If
that interface is removed or overwritten, the host will reconfigure
another secondary interface with the same IP address when it receives
the next router advertisement. Alternatively, the router can be
configured to stop advertising the prefix that corresponds to the
offending IP address.
Removing An Interface
A primary interface cannot be removed from the system until all
secondary interfaces are removed. You can remove secondary interfaces
from the system using the ifconfig inet6 command, as in the
following example:
ifconfig lan1:1 inet6 ::