Question about using multiple IP phones for the same extension?

This has always confused me. I remember a year or two ago when someone was trying to sell me a VoIP system with SIP they were showing all these benefits like having your office phone, but also having a WiFi handset for when you’re working remotely and so on.

I purchased a WiFi phone a few months ago but from my experience, it seems like whatever phone, whether it’s an IP phone, softphone etc, registers last, that’s the one the calls usually go to but not always.

Like for example, when testing a phone in the office, I used X-Lite and connected as the conference room extension. When I’d call the conference room from my phone, only X-Lite would ring. However on the 2nd or 3rd time that I called it, the actual conference room rang and X-Lite didn’t, even though X-Lite could still make calls. When I had my WiFi phone, if I connected as my extension, all calls went there as well.

The reason I’m asking is because I was thinking it would be nice to buy a SIP phone to have at my home office for when I work from home, instead of having to use my cell phone. The thing is, how can I choose where my calls go? When I had the WiFi phone, I just made my office extension 1234 for example, then the WiFi phone was 12345 and I used follow me to have it ring incoming calls on 1234 and 12345 at the same time, but that just seems like a lot of work to accomplish this. Just wanted to find out if that’s correct or not, thanks!

Check out the wiki for Asterisk 1.8

That describes shared LINE appearance (SLA) and not shared call or shared extension appearance to which I believe the OP was referring.

The feature you’re looking for is a shared call appearance (or in other circles, shared extension). This feature is not available on Asterisk. You cannot have two extensions “1234” register at the same time. The last one to register would get the incoming call. The only thing you can do is set up a ring group with distinct extensions in it and use the “ringall” strategy so that all registered extensions in the group ring on an inbound call. The “follow me” feature accomplishes the same function as mentioned.

Most proprietary phone systems like Avaya, Cisco, Nortel and Siemens support bridged extension/call appearances for multiple phones with the same extension. The Asterisk community apparently does not consider this featuer a priority for the product in their marketplace.

I realize this is a year old, but for the sake of search results I thought I would add another option. I’ve been looking for this functionality too and it seems the only supported way is by using FreePBX 2.9 (appears to also work in 2.8 with manual tweaks) addition of User/Device mode:


Why wouldn’t you just set up several different extensiont that all ring together in a group. If you don’t want the extension in your office to ring when you aren’t there forward calls from it to the extension that you will have with you. I have never played with follow me but I get the impression that it is intended for this type of requirement.

i know if use device and user mode, multiple phones can share the same extension, but all the phones are registered by the same account.
now i want multiple phones share the same extension, and all the phones are independently of each other. they just use the same extension number.

just like:
i have a extension number 2001 in two or more company(A and B and …). but they can not influence each other. they just have the same extension number.

can it works? thanks


  1. Use a ring group or follow me for now.
  2. Multiple registrations works with Asterisk 12 but a bunch of other stuff may or may not work. 13 is the magic number, watch for it’s release.
  3. Device and user mode doesn’t exist don’t use it, things break and as we progress more things will break.


I understand using the Ring Group technique for handling multiple devices (physical phone, soft phone, etc.) and ringing the devices simultaneously by calling a Ring Group number. I also understand creating dial plans directly in Asterisk .conf files to accomplish the same thing, but now I am working with Asterisk-12 and FreePBX-12(beta).

Could you elaborate a bit about Multiple Registrations on the “12” platform, specifically using FreePBX-12 and Asterisk-12 to utilize Multiple Registrations.

i think your best bet is to use follow me

So as 13 is out and the latest FreePBX is running 13 - has this changed?

Is there a way to get the shared line functionality?

SLA is not a feature of asterisk. I doubt it ever will be

No not even in 13

I think there is some confusion, SLA will never be a thing officially. PJSIP supports multiple endpoint registrations and is available in Asterisk 12 and 13. This is NOT SLA

Under the the (PJSIP) extension you will see:

If you have 3 devices this # would be 3…

1 Like

Let me make sure I understand -

  • SLA would allow two phones to register and one could pickup either or both and be connected to the same call. This is not supported (and looks like it will never be supported)

  • Multiple endpoint extension registrations in PJSIP would ring both endpoints and the one picked up first would be connected to the call.


That is correctly.

However people seem to associate SLA with “on hold sharing” which pjsip does not support.

[quote=“kenn10, post:4, topic:9815, full:true”]
The feature you’re looking for is a shared call appearance (or in other circles, shared extension). This feature is not available on Asterisk. You cannot have two extensions “1234” register at the same time. [/quote]

It might be difficult on FreePBX, but it is certainly available in Asterisk. The problem that FreePBX imposes is that it confuses devices (equipment numbers) with extensions (directory numbers), and requires devices to register under their extension number. Systems that allow multiple phones to share an extension number and ring together generally make a clear distinction between equipment and directory numbers.

Registering under extension numbers is actually bad security practice, as it removes part of the guesswork for attackers.

“possible”. Yes. What people want? No.

Also “systems that allow multiple phones to share an extension”. What people usually think is shared hold. That is not what that means (without using sla.conf see below)

It specifically states in the documentation that SLA doesn’t support transfers. So while you’d have shared hold ability you wouldn’t be able to transfer a single call. Seems broken or useless in my eyes.

You should be running some flavor of intrusion detection such as fail2ban which makes this less of an issue.
You should be using complex passwords which in conjunction with the above should make this a non issue.

To see how “good” your password is checkout: