What is a dial plan?
A dial plan is a set of instructions for Cisco and LinkSys IP phones. It is what allows and restricts the device from making certain calls to certain numbers. They may seem very complicated but when broken down they can become easier to understand. While some dial plans seem very convoluted, there are much simpler plans you can set in order to set up just to do certain things. For example:
All dial plans are entered in brackets like this: ()
This is the dial plan we would recommend for most users, as it allows you to dial anything you wish, whether it be a short code or physical number, international numbers included:
This indicates that an infinite amount of numbers can be dialled for any short code OR for any number. Let’s break it down:
The *x. (asterix) is the button pressed at the beginning of a short code. For example *72 or *74 while the x. means an infinite number of digits can be dialed when dialling a short code. For example: *1, *12, *1234, *12345678 etc
| - The bar/pipe symbol is computer speak for OR.
x. means that any number can be created and that any number can be dialled an infinite number of times. For example: 01234 567890. Even international numbers can be dialled without restriction. For example: 1 800 12345 or 00 123456 78912.
Now what if you wanted to start restricting certain numbers or only call certain numbers like 999 or 111?
This is certainly possible! Another example would be this:
This would mean that any number can be dialled that ends in 99 so: 099, 199, 299, 399, 499, 599, 699, 799, 899 and 999.
To restrict numbers being called, square brackets  are introduced. For example:
This means that you can dial a certain range of numbers before the digits 11. In this case, you can only dial 111, 211, 311, 0 or 00. You could also write this range as [1-3]While there are many other constraints and restriction types available, these are just a basic few.