Enumeration and Registration
Network port scanners can be used to enumerate SIP User Agents, Registrars, Proxy servers, and other SIP-enabled systems. SIP usually listens on TCP or UDP port 5060.
Other protocols required for VoIP calls, such as RTP, listen on static/dynamic ports other than port 5060. While port 5060 is used to set up the session using SIP, the actual media transmission uses other ports.
Enumerating SIP Devices on a Network
Here's how to enumerate SIP devices on a network, step by step:
Download Nmap from http://insecure.org/nmap/.
nmapon the command line (Windows) or shell (Unix) to retrieve the syntax of the tool.
Enter the following nmap command on the command line/shell to enumerate SIP User Agents and other intermediate ...