Two devices registered to same extension

Just a simple (perhaps silly) question :
I realized that two devices are (erroneously) registered with same credentials on the same SIP extension and they also can work together at the same time
Why is this ?? Devices and Users are not enabled neither PJSIP
Any idea ?

You can do it but whatever extension registers last is the only one that will receive calls.

They could both dial out though.

Is it an asterisk related behaviour ?
Mainly for security reason (if not by mistake like me) other SIP pbx refuse registration over an already registered extension.
Could this “feature” be avoided ?

They cannot both be used at the same time. Whichever one registered last will get the calls. This is a characteristic of Asterisk and the way it handles SIP using Chan.SipC. Once you switch to PJSIP, you’ll be able to have multiple devices registered using the same extension number.

You can accomplish the same effect right now fairly easily, however.

  1. Set-up Extension 4001. Set the CID Num Alias to 400. Enable voicemail and set password.
  2. Set-up Extension 4002. Set the CID Num Alias to 400. Set Mailbox to [email protected] Do not enable voicemail.
  3. Create a Ring Group 400 that rings 4001 and 4002.
  4. Create a Paging Group *80400 that pages 4001 and 4002 (I haven’t tested this last item, so it may not work, but the rest will).

Now, if either extension calls out, it will show 400 as its extension number, and if anyone calls extension 400, it will ring extension 4001 and 4002. Both phones will display voicemail from extension 4001. You may have to program 4002’s VM key to dial *984001 instead of *97.

The question was about disabling at all the double registration chance, just to avoid any other device knowing sip user/pass can create troubles…
Anyway, thank you for hints.

In each extension

deny = 0.0.0.0/0.0.0.0
permit=a.b.c.d

and statically assign all your phones. For remote phones, expand the permit to the network they are in.

1 Like