NOTIFY Failed: Not Authoritative for notify zone

[Ashwin Kotian]

I've setup a Split DNS server on Redhat Linux 7.1 which is running 2 
daemons (internal & external servers ). Everytime I start the BIND 
services, the daemons start up & run successfully, but there is always 
this message which often gets repeated in the logs:

notify failed: not authoritative for notify zone (REFUSED)

What is the reason for this happening ?

My internal DNS server is serving 4 zones ( 2 private zones & 2 pubic 
zones ) while the external DNS server is serving 2 public zones (same as 
the ones served by the inetrnal DNS server). So effectively both DNS 
servers are masters for the 2 common zones. For the 2 common zones, the 
zone files for internal server contains address entries with regards to 
internal IP addresses while that for the external server contain 
global/public IP addresses.

Any solution/suggestions in this regard is greatly appreciated.

Thanks,

Ashwin.