Tcp/1719 is part of the H323 Gatekeeper default ports (which can be changed) Tcp/1720 is the H.225 call setup port, and I haven't heard of this being a configurable port. HTH, Scott Morris, MCSE, CCDP, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIP, CCNA-WAN Switching, CCSP, Cable Communications Specialist, IP Telephony Support Specialist, IP Telephony Design Specialist, CISSP CCSI #21903 swm@emanon.com -----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] On Behalf Of Joe Shen Sent: Thursday, November 11, 2004 6:40 AM To: NANGO Subject: How to Blocking VoIP ( H.323) ? Hi, How could it be done to block VoIP at access router? I've thought about using ACL to block UDP port 1719,but this could be overcome by modifying protocol port number. regards Joe __________________________________________________ Do You Yahoo!? Log on to Messenger with your mobile phone! http://sg.messenger.yahoo.com