asterisk users - Aug 2005 - Single extension/user registers across multiple asterisk servers

Hello ,
I have a question which i am not clear that whether it is possible or
not so i want some help to clearify Sorry for very long mail:
we have eight asterisk servers across different cities connected
through IAX intenet connection is DSL broadband so for sake simplicity
and easiness for eight servers i assigned particular/fixed extensions
dial patterns for example 1XXX for Server  1,2XXX for server 2 and so
on upto eight servers this setup works fine now one user  let say
register on server 1 move another location for example in server 2
domain  what i want to do when user1 moves any location upto 7 other
locations its user/extension remain same i.e. SIP/1001 and when this
user connected it becomes local user but its identitity not change .
The reason for doing that if user1 moves to any other location it
registers to its own server i.e. server1 and it is physically
connected in the domain of server2 so user1 dials the 2XXX extensions
i.e. on server2 the call first goes to server1 which resides in
another city/location then server1 routes the call to server2
logically this is right and exact way but physically it is very funny
is this possible means dial plan sharing every single user registered
on multiple locations automatically everytime he/she connected to that
location so in this way he/she will be the local user for that
location and saves lot of precious bandwidth .
Sorry for very long question but right now i am stuck i think this is
possible but how i am looking wiki alot DUNDI,ENUM etc but fails to
decided whether it is possible or not.
Sorry for bothering
Thanks In Advance.