Lately I've tried to figure out a couple of ways to have a redudant master setup of BIND. BIND itself doesn't have any features to support this which has been bothering me as it would be useful to fail over to a secondary slave.
After numerous discussins on the bind-users list I've reached the conclusion of how I would do it, described in the picture to the right.
BIND slaves is able to notify other slaves when changes occur. To utilize this I would have 1 primary master, and a secondary master which acts as a slave towards the primary. Both of these servers wouldn't allow queries from clients but they would feed the slave-servers acting as DNS-servers for clients on the network.
Unfortunatly this doesn't solve the entire problem as the slave doesn't take flags such as allow-update, or update-policy. The best way to solve this is most likely going to be some kind of script syncing the primary config to a standby file at the secondary.
I'll be working on this solution the coming weeks and post further info I gather along the way.