System information

In the UK, you might need something more like this:
_0[123789]XXXXXXXXX
_0[123789]XXXXXXXX
And in Australia, your dialplan might have these pattern matches:
_NXXXXXXX
_0XXXXXXXXX
Please don’t just copy and paste these pattern matches into your
dialplan. The peculiarities of regional dialplans are tricky, and change
constantly. One important item that needs to be carefully considered is
the region-specific number for emergency calling, as discussed in
“Emergency Dialing” on page 154. You don’t want to get this stuff
wrong.
The North American Numbering Plan Authority
In much of North America, the North American Numbering Plan (NANP) is in use. All
countries in the NANP are assigned to country code 1. Canada and the US are the most
well-known of these countries, but the NANP actually includes around 24 different
countries and territories (mostly in the Caribbean).
ENUM
In order to allow the mapping of E.164 numbers onto the DNS namespace, a way of
representing phone numbers as DNS names had to be devised.
This concept is defined in RFC 3761, helpfully named “The E.164 to Uniform Resource
Identifiers (URI) Dynamic Delegation Discovery System (DDDS) Application
(ENUM).” ENUM reportedly stands for Electronic NUmber Mapping.
According to the RFC, converting a phone number into an ENUM-compatible address
requires the following algorithm:
1. Remove all characters with the exception of the digits.
For example, the First Well Known Rule produced the Key
"[phone]". This step would simply remove the
leading "+", producing "442079460148".
2. Put dots (".") between each digit. Example:
4.4.2.0.7.9.4.6.0.1.4.8
3. Reverse the order of the digits. Example:
8.4.1.0.6.4.9.7.0.2.4.4
4. Append the string ".e164.arpa" to the end. Example:
8.4.1.0.6.4.9.7.0.2.4.4.e164.arpa
Clear as mud?
248 | Chapter 12: Internet Call Routing