Using the same sasldb2 at master and slave

Hi,

still playing with replication and found another thing I'm not sure how
to solve: is it possible to set a default REALM in imap.conf? I'm
running a simple master/replication setup. The master authentication
with local /etc/sasldb2 containing userIDs like
tetstuser@hostname-master. I want to keep the authentication simple
without a central database. If master goes down I have to switch IP or
change DNS record and copy the master's sasdb2 database from backup to
slave. Problem now: the authentication there will not work because the
slavehost itself is running with another hostname and imap logins are
locking for tetstuser@hostname-slave in the sasldb2 now and will not
find those users. In other words: I have a master and a slave with two
different hostnames, but want to use the same sasldb2 in copy without
having duplicate userIDs like tetstuser@hostname-slave and
tetstuser@hostname-master in it. Possible?

Ciao!