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Thirdlane

Caller ID Filtering

Caller ID Filtering is the number-oriented way to control who can call in. You add a number, and the system either rejects calls from it or — in allow-only mode — treats it as one of the few numbers permitted through. It writes the same rules as Inbound Permissions, so anything you add here shows up there and the other way around. Use this screen for numbers and that one for raw dialplan patterns.

Enabling checking

Filtering rules are stored whether or not checking is turned on, and they only affect calls once the Dialplan Variable TL_CHECK_INBOUND_PERMISSIONS is set to 1. While it is off, the screen shows a notice, and a system administrator can turn it on with the Enable Checking button. Tenant administrators do not see the button, because the variable is global — they see a notice asking them to contact their system administrator instead.

The two modes

The mode decides what happens to a caller who is not on the list. The Mode selector above the grid shows the mode currently in effect; picking the other one asks for confirmation first, because it flips how every unlisted caller is treated.

Block listed callers (the default). Listed numbers are rejected; every other caller gets through. This is the usual choice for cutting spam and nuisance calls.

Allow only listed callers. Listed numbers get through; every other caller is rejected. Use this only for a line that should hear from a known set of callers, and remember that it also rejects legitimate callers you have not added yet.

Adding a number

Number. The caller’s number, in either international form (+15551234567) or national form (5551234567). Separators such as spaces, dashes, parentheses, and dots are ignored.

Each entry is saved in both international and national form, because whether a trunk delivers Caller ID as +E.164 depends on the trunk and on whether inbound normalization is enabled for it. Storing both means the entry matches either way.

A value that starts with _ is kept verbatim as a dialplan pattern rather than being expanded. For anything beyond a single number, Inbound Permissions is the better screen.

Description. A free-form note — why the number is on the list, who reported it, when it can be removed.

How matching works

Asterisk always prefers the most specific matching extension, so an entry for one exact number always wins over the broad catch-all that covers everyone else. There is no rule ordering to manage, and adding a number never requires re-sorting the list.

Caller ID is checked after inbound E.164 normalization, so a normalized +E.164 caller ID matches the international form of your entry. On a trunk without normalization, the national form matches instead.