Solved SIP Trunks and Channels

[brendanr]

Hi all,
Trying to get my head around this!
We have a 4SC license, with 2 SIP trunks each with 1 channel.
How is it possible that we can be on 4 external calls at the same time? My understanding on SIP channels is that each channel acts a single phone line, so surely we should only be able to be on 2 external calls at any one time?

Also, I have an outbound rules that says all extensions use a certain SIP trunk to call out on, but again looks as though I can make 4 outbound calls at the same time. How are the SIP trunks and channels related? I'm new to this!

Thanks in advance!

 

[YiannisH_3CX]

Hi @brendanr

So your 4SC license will allow you to have 4 simultaneous calls so the question is why does your SIP Trunk provider allow you to make more calls that the channels on your trunk?
You can also limit the channels of the SIP trunks from 3CX. Just edit your SIP Trunk and se the "Number of SIM Calls" to 1.
That will impose the limit from 3CX and not from the providers side.

Also make sure that all 4 calls are external because internal calls between extensions also count as sim calls.

 

[Saqqara]

Simultaneous calls includes internal to internal calls.

 

[brendanr]

Hi @brendanr

So your 4SC license will allow you to have 4 simultaneous calls so the question is why does your SIP Trunk provider allow you to make more calls that the channels on your trunk?
You can also limit the channels of the SIP trunks from 3CX. Just edit your SIP Trunk and se the "Number of SIM Calls" to 1.
That will impose the limit from 3CX and not from the providers side.

Also make sure that all 4 calls are external because internal calls between extensions also count as sim calls.

Thank you - it appears that our SIP trunks weren't actually single channel (our provider got it wrong). Starting to make sense now, thank you

 

[SteveITS]

our SIP trunks weren't actually single channel (our provider got it wrong).

I've seen some SIP providers use odd terminology, such as having one order "2 call channels per trunk" and 4 of those "trunks" get 8 calls. But in the end the ones I've dealt with is really one trunk with multiple channels/calls.