When Regular Expressions Are Involved - Snom ONE IP Technical Manual

If the trunk's Send call to extension field is empty and the system finds an extension
that is associated with the number that was called, the called number will be reflected in
the user portion of the Request-URI is
Figure 4-11. SIP INVITE Reflecting DID Routing

When Regular Expressions are Involved

Regular expressions can be used for numerous call routing purposes, but they are es-
pecially helpful when you have a large number of DIDs. When you have a few DIDs,
you can simply enter the DID number into the Account Number(s) setting in the
extension that the DID is assigned to. Assigning a large number of DIDs to individual
extension accounts, however, is cumbersome and can be expedited through the use of
regular expressions (direction inward dialing is discussed on page 124).
A regular expression is a special character string that describes a search pattern that the
trunk will use when looking for a match for an incoming number. The expression con-
sists of the following key elements:
•
Pattern: The pattern portion of the string defines the numbers that the sys-
tem will use when searching for a match and how many. In the example shown
in Figure 4-12 (expression 1), the system will consider all numbers (0 through
9) when identifying a match and will include only the first seven digits. In
expression 2, the system will still consider all numbers but will include only
the last three digits.
Chapter 4: Trunks
8124351234 (Figure 4-11):
121