How to solve not used extensions, incoming calls to forward external numbers (cellular user's number)


Product: UCM-62xx
Platform: Grandstream UCM

How to solve hasn’t used extension incoming call to forward external numbers (cellular user’s number)
My solution is one SIP number which is working on UCM 6208, Behind on UCM working 3 extensions those extensions will be incoming calling answered, but not used extension numbers only used own cellular mobile numbers. Those cellular numbers will be answered incoming calls.

Extension - Call Transfer - Call Forward Unconditional is only working the extension online which means connecting to server. If an extension offline disconnects from the server then incoming calls don’t transferred to external numbers, then UCM answered “No available agent”

What kind of configuration to fix my solution?

Thank you. :slight_smile:

The follow me option as external numbers with a static order. I need dynamic order with a strategy

first of all you have to solve the problem of the unregistered extension, secondly each extension with which mode is diverted externally?


use an fxs extension and see how that goes for you…



I need to know how the calls reach the extension(call flow)
ring group
direct dial


what does FXS mean? it likes working virtual extension or ghost extension ?


I’m using ring group and queue, IVR but don’t know direct dial. what is that ?


FXS extension is good but only two and can’t transfer call.


FXS is an analog extension that goes to a physical device like a fax machine or analog phone.


Any extension that is rung via a ring group or call queue will ignore call forward unconditional rule.
They don’t want a single extension to be able to hi-jack an inbound route.
If you want to use a cell phone in a Ring group you will likely need to use a soft phone like GSWave.

If you call that one extension directly the call forward should work.


mmm okay. I don’t neet physical device. My costumer want yours calls receiving on his own cellular cell phone. I’m little confused how to transfer those it must using extension ?


those are including 3 extensions in queue. why it’s working because it (Any extension that is rung via a ring group or call queue will ignore call forward unconditional rule.)

Costumers dislike using GSWave and other soft apps.

How to solve this requirement ?


that is good working. how to solve this requirement?

                             1001 (not used extension) -> Call forwarding to (External number as cell phone.GSM)

SIP(XXXXXXXX) -> 1002(not used extension) -> Call forwarding to (External number as cell phone.GSM)
1003(not used extension) -> Call forwarding to (External number as cell phone.GSM)


The simplest way may be to let the person calling in pick who they want themselves.
Send the calls to an IVR that lists the extensions as options and calls the extension numbers directly(no groups or queues). Then the call would go to the extension number and immediately forward to the cell number.


it is not bad choice but costumer requirement doesn’t want this way. Don’t want IVR and choose numbers. it behind company strategy the incoming calling must linear or and random giving to workers cell phones. :frowning:


I understand the dilemma, I don’t have a good workaround with Grandstream for that. I know Asterisk(which Grandstream is built on) can override the setting and allow a ring group call to forward, but that feature isn’t made available within Grandstream.


What is maximum time condition in UCM inbound role ?


RG can forward calls if forward is set.
Just need mark this.

But forward will not use USER privilege so special routing is required for security reason.
Outband with Custom Dynamic Route (for RG number afair) and pattern that match desired mobile phones. This will prevent RG call anything else.

I do not tested it lately but customers was able do it itself :slight_smile:


Hello. @Marcin @lstutesman.

My flow diagramm
call incoming then - SIP-Trunk-> IVR -> press 3 -> Extension (the extension never go to online then Follow me external number {Mobile phone number}, ) it is doesn’t work but external number set in Key Pressing Events in IVR then is working how to solve it ? thank you


What error you get ?
Catch Ethernet capture and see what you sent to Provider.
For this u can use “shadow” trunk (same as original but tweaked so call is set properly for some functions) if you have problem with setting caller-id etc.


Thanks. is this solution possible in UCM 6208 ?