Typically we’ll get a main branch with 30-50 employees then a few remote offices with about 5-10. I figure inbound and outbound its best to use local pbx or SIP trunking. But internal branch to branch is where I’m wondering is best. If we set each branch to a different extension block of numbers (main 1000, branch1 1100, etc) then use something to connect the phone systems together with trunking. Just not sure the best way.
I figure if they only have 1-5 phones we’d just VPN the phones to the main pbx as it’s not a huge deal if their phones are down when HQ is down.