[Samba] Samba PDC and a backup PDC in a different LAN - how?

[Tomasz Chmielewski]

Hello,

I have a setup like that in almost 20 branch offices.


internet
   |
router
   |
switch
   |
workstations, "Samba PDC + OpenLDAP"


usernames/passwords are synchronized using LDAP with a central server.

Roaming profiles are backed up to this central server once a week.

Each branch office is connected with each other using VPN.


Now in case if this "Samba PDC + OpenLDAP" breaks, I would like to allow 
users to work.

This means they should be able to log in to that central server directly 
over VPN (which means slowness, but that's OK during a general failure).

Could you guys give me some hints how to do this?


Tomek