Proxy

Hi,
I’m running microsoft proxy 2.0… On a winnt4.0 server.
Is there a way to see a listing of what ports are open and what is assigned to them. Also I have to open ports tcp 50,51 also port tcp 500.. As I understand I have to check “Enable Packet Filtering on external interface” and also Enable Dynamic Packet Filtering of Microsoft Proxy Server Packets”. As of now neither one of them are checked, and right now our internet access is working fine. If I do check the above and add the ports above will that effect the current status of the internet for the users.I hope I explained this right. Any help with either question would be appreciated.