Understanding Route Patterns of Call Manager

The core of any telephony service is to access the numbers they want to dial.
In the CUCM there are 3 main components to build a dial plan.

1. Route Pattern
If someone dials a number which matches a configured route pattern, that call is eligible for routing.
Ex:- XXX, 9.XXX, [1-2]XX, 234!#

2. Dial Plan Hierarchy
This is what tells the CUCM to route the call to the specified destination.
Ex:- route 911 calls to external gateway..

If you want to know about Dial Plan Hierarchy click here.

3. Class of Control
This controls the calling abilities of phones.
Ex:- A lobby phone should not be able to take IDD calls..

If you want to know more about Class of Control click here.

In this post, let's discuss about Route Patterns and their usage in common.

Lets get a simple example of XXX, X can be any digit. it is called a wildcard.

When someone dials a number, let's say 911, 9 matches the 1st X, 1 matches the 2nd X and final 1 matches the final X. if XXX is configured as route pattern and if someone dials 911, that call is eligible for routing. X means any digit, that means any 3 numbers can be routed using XXX route pattern..

When a shorter pattern matches the beginning of a longer pattern, calls to the shorter pattern will be delayed by the inter digit timeout (t.302 timer).

Ex:- Let's say we have 2 route patters configured..

XXX
XXXXX

If some one dials 911 now, it will be delayed to process because CUCM thinks the user may be dialing the 2nd pattern.. This delay is the t.302 timer which is default to 15 seconds and can be changed manually at Unified CM Administration > System > Service Parameters, select the server and the service as Cisco CallManager (Active).

Under Clusterwide parameters, you will find it.

You can configure a route pattern to exactly match 911 and set Urgent Priority Tick under route pattern configuration to route the call right way ignoring t.302 timer.

Companies use access codes to differentiate between internal and external extensions.

Ex:- 9.XXXXXXX

When you start dialing with 9, CUCM thinks it is an external call now.
So there cannot be internal numbers starting from 9 in the company..

Ofcourse this 9 must be stripped away when you route the call out from your network to public telephone network which we call 'digit manipulation'. To do that chose 'Discard Predot on called party transformations'

As soon as you hit 9 a second dial tone comes from the CUCM. We need to configure it from CUCM, tick Provide Outside Dial Tone. You can see it is ticked on above screen shot.

Now let's think another possibility..

If someone dials 911, it should be routed externally but people may not remember to dial an additional 9 before 911. So following 2 route patterns must be configured..

911
9.911

Now what about other service numbers like 211, 311, 411? Following route pattern must have to be configured to match them..

9.[2-9]11

This says the 2nd digit can be any number between 2-9

If [257-9] is there that means the digit can be 2 or 5 or 7 or 8 or 9..

Now what will be matched if someone dials 9911 from following route patterns?

911
9.911
9.[2-9]11

It will match the 2nd one because it is the best match as the 3rd one has 8 more combinations..

When a number matches more than one pattern, the pattern with the smallest number of possible matches is selected.

Ex:- 1234 is dialed and following route patterns are configured.

[1-5]XXX
[1-2]XXX

2nd pattern is selected as it has only 2000 possibe matches compared to the 1st one which has 5000 possible matches.

Here are some other wildcards..

9.011!

'!' means there can be any number of digits so if someone dials 9011234567 CUCM will wait for t.302 timer and route the call. To stop t.302 waiting time another wild card can be introduced.

9.011!#

'#' means the user has end dialing. So if 9011234567# is dialed, the call will be routed right away..