You might face issues with zone transfer to ipv4 secondaries on a dual stack server where the bind listening on IPv4 and IPv6 address,
client ::ffff:11.11.11.11#43253: zone transfer 'example.com/IN' denied
this happens because , once the v6 is enabled on bind it just try to make ipv4 address looks like v6 address.
Solution : just add the v6 formatted v4 address to the allowed list
allow transfer { ::ffff:11.11.11.11; };
./arun