Hi JimNX!
On traditional systems, you'd have 1, 2, 3, 4, or however many separate phone ("CO") lines entering a building and running to the PBX. If configured for it, any extension could choose to pick up L1, L2, L3, etc... I haven't found a way to do this with 3CX yet. Is this not possible anymore? I researched it a bit and a lot of what I read said that 3CX supports only 1 DID to an extension.
This is commonly referred to a Shared Line Appearance. The definition of this is that phones can monitor the
Line coming into the system and then certain extensions can monitor this line and pick it up.
3CX does support Shared Line Appearance in the sense that you can't monitor the Line, but can monitor calls going to
Extensions. This means that depending on your use-case, you could make things work.
So, what you could do in 3CX is configured your Inbound Rule for number DID_1 to be routed to Ext 100 (Receptionist). Then on other Extensions that you would want to be able to 'intercept' calls to Ext 100, if they have IP Phones you can add Ext 100 as a BLF key and by pressing it, they can answer a call that is currently ringing on Ext 100. This of course can also be done through the 3CX Windows App and Web Client.
The distinction here is that 3CX can monitor an Extension, not a Line.
I'm using Twilio as my SIP trunk provider. Twilio supports multiple DIDs per SIP Trunk, but again, I don't see anything in 3CX that supports or takes advantage of this. Does that mean I should be using 1 SIP trunk per DID? I don't know if that's overkill or best practice. I'm thinking of a SIP Trunk as an account -- I wouldn't set up separate accounts just to have different phone numbers, you know? Do I have this wrong?
You can add multiple DIDs under a single SIP Trunk as explained here:
https://www.3cx.com/docs/twilio-elastic-sip-trunking/
So, your single SIP Trunk will register once with Twilio, and through this one Registration, Twilio will be sending you all calls made to the numbers you have under the same account (assuming you have configured this in the Twilio portal correctly as well).
The only other thing you need to do after this is create Inbound Rules for each one of your DIDs so that you set where calls to each DID should ring:
https://www.3cx.com/docs/manual/inbound-did-call-routing/
In regards to SIP Trunks, is it bad practice to have several of them, rather than running multiple DIDs through one?
Having multiple accounts/SIP Trunks from the same provider, in my opinion is not very useful. Especially in the case of Twilio and most other Registration-based providers, even with a single Account, there is redundancy as the Registrar they give you resolve to multiple IPs and 3CX will switch between them if it detects that one is down.
Having a second SIP Trunk from a different provider for redundancy purposes could be a good idea, in case you want to be covered in the event that your Primary provider goes down completely.
