Telephone system "VOIP" - Asterisk
The school I am working on is considering to replace the really old " analog lines " telephone system and we are looking at all different possibilities.
Our school is mostly running Open Source solutions, so we are considering of using Asterisk and FreePBX. Is there anyone using it that could give me some kind of feedback? As telephoning is really important in a school, the school would like to "know" real cases where this system is in place. We are looking at other business solutions as well, but we are not that convince on paying licenses to expand the system later on or forcing us of using their specific handsets, and we would like to set up the system using our current infrastructure.
Do you use ISDN lines or a SIP trunk for the external calls? A SIP Trunk seems a good solution, but we do not trust 100% our internet connection and we would like something that can still work when the internet is down. I currently have a test environment set up and anything to do with internal calls, etc looks quite easy, however I am not familiarized with the set up for external calls with different ISDN lines or multiple numbers and SIP trunks. I would really appreciate any guidelines or resources that could help me on this matter.
Further more, what is your backup/DR plan on this type of systems? Do you currently have UPSs on every switch cabinet to keep the telephones working?