controlling recursion

[Jon Leeman]

I have three name severs;

203.98.224.66
BIND 9.2.1 [MASTER]
Linux Mandrake 8.0

203.98.225.9
BIND 9.3.1 [Slave]
NT 4.0 SP6a

203.98.225.10
BIND 9.3.0 [Slave]
Linux Mandrake 10.0

with;

allow-recursion {
                 203.98.224.0/23;
                 localhost;
                 };

inside their respective 'named.conf'.  They are standard configurations 
  with no views etc..

My problem is the master is allowing recursion from outside our networks 
stipulated but the slaves are not.

I am currently not in a position to upgrade the Master's BIND version to 
the latest.

I'd appreciate any pointers as to what I am doing incorrectly - to stop 
unwanted recursion -  and will supply the full details / configurations 
off list if needed.

Thanks,

Jon