Is it possible? Asterisk without SIP only LAN and softphones


I’m new to voIP, and wanna try it.
My question is: Can I use Asterisk with only softphones in my LAN and no SIP-provider?
If yes: is it possible to use the previous configuration with analog lines?
(This would be a development to a small company: first trying, than replacing the analog phones, but keeping the analog line inputs and lastly changing to a SIP-provider)

Secound question is if anyone tried the Asterisk in Zentyal? I set up to a spare server without any problems…

Thanks, for Your answers
TeeCee : o )

you can use Asterisk with softphones only and no sipprovider. You can only do internal calls to each other but it works.

I have no experience with Zentyal.