Shorewall users - Oct 2003 - Clear and list hosts in a zone

Hi,

I want to control a list of IPs which can connect to my VoIP (tcp port
1720). However, the clients does not have fixed IP address, so I plan to
create a zone called h323zone and allow hosts in h323zone connect to
port tcp 1720.

I know I can use "shorewall add eth0:host h323zone" to add a client IP
to the zone, but can I clear or list hosts in the zone?

Any better alternatives for my scenario?

Thanks,
Martin Chan