options {
allow-transfer {Secondary Server IP; }; allow-recursion { 127.0.0.1; A.B.C/24; }; };</>
In secondary server:add to options:
allow-transfer { none; }; allow-recursion { 127.0.0.1; A.B.C/24; };
options {
allow-transfer {Secondary Server IP; }; allow-recursion { 127.0.0.1; A.B.C/24; }; };</>
In secondary server:allow-transfer { none; }; allow-recursion { 127.0.0.1; A.B.C/24; };