I've been playing with VOIP Linking over the years with programs like ILink, EQSO, IRLP, and Echolink. I tried Allstar many years ago, but was discouraged due to my lack of Linux knowledge and that there was not much documentation on the web. Well things have changed and I now really appreciate what others have shared.
Allstar is now by far my favorite..
The Allstar web site to get started is: https://allstarlink.org. On that site you will find much information as well as the ability to register with Allstar. Once registered, you can request server and node authorization.