Neighbors
in the ND Cache are Not Translated
In our example, there are hosts behind the firewall
with host identifiers :1, :2, and :3. If the prefixes of those hosts
are translated to a prefix that exists beyond the firewall, and
if those devices also have host identifiers :1, :2, and :3, because
the host identifier portion of the address remains unchanged, the
resulting translated address would belong to the existing device,
and an addressing conflict would result. In order to avoid a conflict
with overlapping host identifiers, NPTv6 does not translate addresses
that it finds it its ND cache.
