PostgreSQL and IPV6

I'm using to computers :
- a laptop under Xubuntu 12.04 with PostgreSQL 9.1
- a desktop under Mac OS X Mountain Lion with PostgreSQL 9.2

After the switch to Mountain Lion, i had a small prob connecting to a
database on my laptop.

Usually when, from the laptop, i connect to the deskop which arn't under
the same LAN, I'm using the IPV6 address of the desktop terminating by
"2559" (by psql or ssh : same IPV6 address).

However when connecting from desktop to laptop, altough the IPV6 address of
my desktop is in my pg_hba.conf,psql rejected the connection because an
address terminating by "18cf" isn't in my pg_hba.conf.

Then i did verify my mac os x setup showing that this address is a valid
one for my desktop, in fact my desktop does have up to eight IPV6 addresses.

After that, i edited the pg_hba.conf on my laptop and everything goes as
expected.

The question is about this IPV6 address terminating by "18cf".
first under Mac OS X Lion, i didn't have this address.

Why, in one direction from laptop to desktop i use successfully :

psql -h IPV6-terminating-by-2559

and the other way, from desktop to laptop this is IPV6-terminating-by-18cf
being seen by the laptop's PostgreSQL ?

--
Yvon