While creating our phone system, we will need to create a set of extensions. Although Asterisk has no such requirement, all these extensions should probably have the same length to give comfort to our users. We must determine the length that we will use for all of our extensions.
When creating extensions, it is often advantageous to group certain extensions together. For example, all sales extensions could be in 200s, support in 300s, management in 100s, and so on. Or we could go further and say that all first-tier support will be in 3100s, the second-tier support in 3200s, third-tier support in 3300s, and so on.
We should keep in mind that it is easier to add extensions when there is an available number than it is to renumber all extensions in a building, because we have filled up all of our available dial strings. For instance, suppose we chose 1-digit extensions and have the following phone list:
0—Operator
1—Reception desk
2—Break room
3—Conference room...