[asterisk-users] sip echo server

[Ali Khalfan]

I'm trying to find a way to setup a SIP server that will mainly echo
back a request from one agent only,

my question is do i need to setup any of the other conf files besides
extensions.conf and sip.conf?

the book says "If you plan on a pure VoIP network, the only real
requirement is the asterisk package," ,

but i'm doubtful about zaptel.

can anyone help me out?