Understanding relationship (many to one?) of DIDs to a SIP trunk

Hello, I am very new to FreePBX, with less that 3 weeks experience. I am still trying to understand the relationship between SIP trunks and DIDs.

I have five DIDs and one SIP trunk. As I continue to learn tis technology, my first goal is to have my initial system be one that “can make as many outbound (originate) calls as I have DIDs.”

With my current configuration which has both PRIMARY and SECONDARY SIP trunks enabled, I can make only ONE outbound call at a time, from any DID. My expectation of one SIP trunk and 5 DIDs is to be able to make 5 outbound calls simultaneously.

My expectation is NOT met with a single SIP trunk and 5 DIDs. So, at this point I either (1) misunderstand the relationship between SIPs and DIDs, or (2) I have not configured some FreePBX control parameter correctly, or (3) the very old PC which runs FreePBX is too underpowered, or (4) some combination of the above.

I can, however, make at least ONE outbound call from a given DID and simultaneously RECEIVE an INBOUND call on another DID.

Here is my question:
“In order to make multiple Outbound calls, do I need a SIP trunk for each of my five DIDs?”

I realize this is a very basic question and will be grateful for a clear answer. I have not as yet found an internet source that is clear about this question.

Update: Skyking 2010 replied: “Bottom line - DID’s are simply phone numbers fed on a trunk. Trunks are usually two way. The amount of concurrent traffic on a trunk is set by your provider.”

I purchased DIDs and one SIP trunk through FreePBX.org online store (Broadband.com).

Can anyone here advise re Broadband.com provision of DIDs/outbound calls per SIP trunk?

Many thanks!


Re “DIDs per SIP trunk”, your description of multiple DIDs per SIP matches my expectation. My expectation stems from (1) concept inherent in the word “trunk” as traditionally used in telephony and (2) my interaction and reading of relevant forum posts.

My SIP account, sourced by FreePBX/Broadband.com shows 1 channel. As another thread, I will try to address FreePBX moderator (assuming there is one) as to how to engage with FreePBX/Broadband.com to enhance SIP account. If no way to do this, change providers in Oct.

Many thanks for your time!

A trunk in analogous to s aingle conventional line, but you can have multiple DID’s (Inbound Numbers) associated with it…kind of like the old party lines.

You need a trunk for each concurrent call.


Thanks Bill,

You may want to look at your SIP subscription and see ow many channels/call appearances your provider is giving you.

A SIP trunk can have as many of those as you want, further there is no direct relation to a DID and how many concurrent calls you can have on a SIP trunk.

This being said, I am sure you can get what you need with your setup.

Just need to look more on your provider side and find out what you bought.

Hope this helps.