How to forward an external VOIP call on busy?

Asterisk Asterisk Support
1

How to forward an external VOIP call on busy?

E.g. we have 3 SIP VIOP lines, when the 1st is busy we want the external call to be forwarded to the next available line.

My VIOP provider tells me this need to be done by our IP PBX software or VOIP box hardware.

Is this possible? If so what is the function called so I can refer to it in the manuals.

Any advice is appreciated!!!

2

Set qualify=2000 by your peers. This will have Asterisk poll your ITSP to see if it is up and alive. I then use n+101 for failover:

exten => _X.,1,Dial(SIP/${EXTEN}@provider-1,20)
exten => _X.,2,Hangup
exten => _X.,102,Dial(SIP/${EXTEN}@provider-1,20)
exten => _X.,103,Hangup