How can I block certain Ports on my router?



I know how to give ueser access to certain ports on my Netopia Router, but how can i block some ports. This I dont know how to do. For example I want to block certain PC's here at work from having any access to the web (port 80) Also, i want to block some users from using AIM. To do that i need to block a certain site on that port. I have all that info, i just dont know anything about BLoking ports. Any help at all would be great. Thanks


google search ip-chains & ip/port masquerading.

should have som3 s0rt of uzerManual for t3h r0ut3r on gitting in & changing the ipchains. usually you can telnet in or someitmes they have a web interface wit t3h r0ut3r.