Which extensions should not be used becasue they are already used for something else

Which extensions are set aside for use by the system and should not be used?

It looks like the following as far as I can see:

7777 is used to simulate incoming calls.
888 is used to barge.
666 is to simulate incoming fax.
555 is used for channel spy.

Is that it, or are there others?


I think you are right, but if its necessary to use one of the list then you need to remove its context from dialplan in extensions_additional.conf, so that number will be free to use.

You can’t edit extensions_additional.conf. It is regenerated each time you make any changes through the gui and reload.


all of these numbers are viewable through the features tab of the GUI so you can see what they are and you can change their assignments if that is what you want to do.

as an added note, if you try to assign an extension to one of these reserved numbers, freePBX will prevent that with an error message telling you that number is already in use.

Thanks for all your responses… I don’t need to use any of these extensions, I was just curious about which ones were actually reserved.

I looked at the Feature Codes page, and the only one I missed from the above list is:


Use the printextensions module to see all numbers that are in use by every module.