How to organize IP telephony for 12 IP phones?

Question

Telephony

The question was asked as part of writing a term paper. It is necessary to implement IP telephony in 1 of the university buildings. You cannot use a cloud PBX, you need a hardware solution.
There are 12 IP phones. It is necessary that employees can make calls within the building, that there is communication with other buildings (you can connect to the general university network by wire), so that they can call IP phones from mobile devices.
I think you can connect to a sip provider or for fault tolerance to an analog line.
I need equipment so that all this can be connected to each other and it works in theory, preferably concrete, because. You will also need to write a cost estimate.
It is necessary to solve this problem with hardware equipment, if possible, write which ports to connect the equipment.

Answer 1

In your case, there are two solutions
1. Server (computer) with installed Linux Server + Asterisk as advised by the respected Drno
2. Hardware IP PBX. I recommend Grandstream UCM6202 (cheap, interface in Russian, configured through a browser) Judging by your comment on the previous answer ("It's just that I'm completely zero in servers"), I recommend this option.
All you need to configure is voip trunks (external numbers), additional numbers (you can immediately have a bunch in a couple of clicks), incoming and outgoing routes - there are a lot of step-by-step instructions on the network.
Further, according to taste (recording a conversation, conferences, voice menu, voice mail and other goodies)
, you wrote that you already have 12 IP phones.
What model?
are they connected to the local network?
Are they on the same LAN segment?

Answer 2

You don't need analog.
To a LAN phone, you can from a POE switch
And a server with Asterix software, for example , We
fasten a sip provider to the server to taste