IAX is the Inter-Asterisk eXchange protocol native to Asterisk PBX and supported by a number of other softswitches and PBXs. It is used for enabling VoIP connections between servers beside client-server communication. IAX now most commonly refers to IAX2, the second version of the IAX protocol. The original IAX protocol has been deprecated in favor of IAX2. The IAX2 protocol was published as an informational (non-standards-track) RFC 5456 by discretion of the RFC Editor in February 2010 (http://www.rfc-editor.org/rfc/rfc5456.txt).

This SonicWALL signature identifies legitimate Inter-Asterisk Exchange v2 (IAX2) protocol NEW connection requests over UDP/4569--retransmitted attempts.