problem with domain and sub-domain configuration

[fddi]

Hello I have one domain

test.com with namserver ns.test.com (10.0.0.1)

and a subdomain

cr.test.com with nameserver ns.cr.test.com (10.1.0.1)


my problem is that if I update hostnames inside test.com zone
updates are not seen by cr.test.com nameserver

they are seen if I restart named on cr.test.com


actually on ns.cr.test.com I have the following directive

zone "test.com" IN {
        type forward;
        forward only;
        forwarders { 10.0.0.1; };
};

but when I update the father zone test.com for example I add an ip address,
the update is not seen by cr.test.com nameserver and I have to restart 
named and after that
it works. So that clients using cr.test.com nameserver cannot see 
updates to test.com domain ip addresses.

I do not know how to fix this problem unless I configure cr.test.com to 
be slave of test.com
but i did not want to do so.

any hints ?

thank you

Rick