Samba password server in different subnet

My current situation:

1 Samba server on the 219.x.y.z subnet (DMZ)
1 Samba server on the 192.168.128.x protected subnet

Both Samba servers running Fedora Core 1, Samba is from RPM of FC1.

I setup the 219 Samba server to act as a password server:

[global]
        workgroup = ABC
        netbios name = INTERNET
        server string = ABC Internet Server
        log file = /var/log/samba/%m.log
        max log size = 50
        socket options = TCP_NODELAY SO_RCVBUF=8192 SO_SNDBUF=8192
        dns proxy = No
        ldap ssl = no
        os level = 33
        preferred master = yes
        domain master = yes
        local master = yes
        security = user
        domain logons = yes

And I want the 192 Samba server to ack as a pass through server to ask for the 219 Samba server to authenticate:

[global]
        workgroup = ABC
        netbios name = INTRANET
        server string = ABC Intranet Server
        null passwords = Yes
        log file = /var/log/samba/%m.log
        max log size = 50
        socket options = TCP_NODELAY SO_RCVBUF=8192 SO_SNDBUF=8192
        dns proxy = No
        wins support = Yes
        ldap ssl = no
        security = user
        password server = host.abc.com # Host name of 219 Samba server

I know that the "password server" option should be a netbios name, but they are on different subnet and the broadcast should be stopped by the router.

I failed.  Any suggestion?  

Thank you.

William WK Lee
Hong Kong