Asterisk has over 60 configuration files, often with very cryptic names.

Asterisk configuration files are small and short in an effort to reduce complexity.

Some configuration files can be ignored depending on what features you are using.

Every call that goes through Asterisk goes through the dial plan.

Every dial plan consists of three major parts: contexts, extensions, and variables

Extensions and channels are two completely separate terms. Don t use them interchangeably.

Macros are an easy way of eliminating code duplication, allowing you to create small functions to automate simple tasks.

Asterisk supports multiple VoIP protocols and numerous hardware connections.

SIP and RTP can be a bit of a security hazard since they require a large number of ports to be open for the audio path of phone calls.

SIP doesn t play well with NAT, but IAX2 does.

FXO connections are for wire connections between the Asterisk server and the PSTN, while FXS connections are for wire connections between the Asterisk server and telephones.

There are two voice-mail applications. VoiceMail(), which supports callers leaving voice mail for users; and VoicemailMain(), which supports retrieving voice mail from the server

Voicemail() can be configured to play a certain message if the user is either busy or unavailable.

VoicemailMain() can be called with a mailbox number...