Does Asterisk work on SIP 1.0 or 2.0?
Yes, although I can’t imagine there are many 1.0 user agents left, and most people require more than just SIP to do anything useful. (OR treated inclusively.)
What is your real requirement?
We want to make sure that our Vicidial is working on SIP 2.0.
I am asking whether it is SIP 1.0 or 2.0?
2.0 is what everyone uses these days, but it should be backwards compatible with 1.0 although I doubt anyone has used it against 1.0.
If we install default Asterisk, it used SIP 2.0. How can it confirm it?
You can look at the signaling…
Ultimately there is no ability to configure whether it is 1.0 or 2.0.