Globalized Call Routing In Cisco Unified Communication Manager Demystified

When deploying a multisite with centralized call processing across multiple countries, the digit manipulation can be complex, since countries use different dial plan.

We need to unify the dial plan in a globalized format +164 so that the employees when they move between Sites (Countries), they still use the dial plan of their country or the (+) as the international code.

Globalization is there to unify the dial plan in order to improve the user experience and simplify the dial plan, troubleshooting and management for the administrator with a single route pattern \+!.

Globalization also simplify features such as emergency numbers, device mobility, AAR (Automated Alternate Routing) and TEHO (Tail Hop End Off).

Now how Globalized Call Routing works?

Let’s take an example.

To call the Phone located in UK, a user should use different format of the PSTN Number, depending the cluster where the user is located, because each country use its own PSTN Access Code and International Code for example:

Countries in EUROPE, users should dial a “0” for PSTN Access Code, followed by “00” for an international call.

In USA, users should dial a “9” for PSTN Access Code, followed by “011” for an international call.

In Australia, users should dial a “0” for PSTN Access Code, followed by “0011” for an international call.

In this example:

From Cluster USA, user should dial 9-011-441519988776

From Cluster EU GE, user should dial 0-00-441519988776

From Cluster AUS, user should dial 0-0011-441519988776

With traditional dial plan approach, in each cluster you need the appropriate and different route pattern for international calls.

In the Cluster USA:

We need a route pattern as follow:

Route Pattern 9.011! pointed to the local Gateway.

In the Cluster AUS

We need a route pattern as follow

Route Pattern 0.0011! pointed to the local Gateway.

In the Cluster EU GE

We need a route pattern as follow

Route Pattern 0.00! pointed to the local Gateway.

The conclusion is that you need a separate route patterns in each site and country.

Now if you have multiple sites distributed over different countries, you will get a different international access codes, also to cover the overall numbering plan within a single country, you may need more route pattern.

Some countries have complex numbering plan, Australia is a great example, let’s say if you estimate 10 routes patterns to cover the numbering plan of given country, then for 100 sites in single cluster, you need 1000 route patterns.

This result is a VERY large dial plan with hundreds or thousands of route patterns, route lists, and route groups to deal with all the variations.

This is not good.

The solution is to use the concept of Globalization based on the E.164 numbering plan as the main dial plan format. E.164 is the global numbering plan. It defines the unique country codes for all countries and specifies that if a number starts

with the “+” sign, then what is expected to follow is a valid country code, followed by a number that defines an individual user within that country.

If we come back to our example, When using globalization, a user dials +441519988776 to reach the Phone in UK,  regardless the location of the user, from USA, from EU GE or AUS, all what you need is single Route Pattern:  \+!

You obtain a simplification of you dial plan, compared to the traditional dial approach.

From the users s’perspective, the globalization should be transparent.

How a dialed digits like 9-011-441519988776,  0-00-441519988776 or 0-0011-441519988776 can match the single Route Pattern \+! ?, if you dont use a tool like the translation pattern, the previously dialed digits will never match the globalized Route Pattern.

Here comes the Translation Pattern in rescue, the Translation Pattern will be used to accommodate local dialed digitss and translating them in a form so it matches our magic \+! Route Pattern.

Just an example.

In the Cluster USA

The translation Pattern is like this:

Pattern: 9011.!

Called Party Transformation

Discard Digits: PreDot

Prefix Digits: +

The call flow is as follow:

User in USA dials 9-011-441519988776, the CUCM find a matched translation pattern 9011.!, the translation pattern is checked first before the route pattern, the system performs Called Party Transformation, it strips the number 9011 because the PreDot, and prefix “+” sign to the resulting number because the Prefix Digits: +, the result is +441519988776.

The transformation from 9-011-441519988776 to +441519988776 is called GLOBALIZATION. Now the new dialed digits match the globalized Route Pattern \+! because the “+” sign.

PSTN does not recognize the “+” sign. For PSTN to accept the call we need another transformation after the call routing decision, here another powerfull tool comes to rescue, we call it Transformation Pattern.

Transformation Pattern is like Translation Pattern, it is used for Digit Manipulations for the Called Party or Calling Party, but the difference is magic!

Translation Pattern is applied before the call routing decision through Route Pattern, while the Transformation Pattern is applied after the call routing decision, in the Gateway configuration of the CUCM, it seems logic because a call routing decision is made, this means a Gateway or a Trunk SIP is selected, here under the Gateway or the Trunk SIP the Transformation Pattern is applied through CSS and Partition.

Our Called Transformation Pattern looks like this:

Called-Party Transformation Pattern

Pattern: \+.!

Partition: From-US-PT

Called Party Transformation

Discard Digits: PreDot

Prefix Digits: 9011

The resulting of the Transformation Pattern is:

The system strips the “+” sign because the Discard Digits PreDot from the number +441519988776, we get 441519988776, then the System prefix 9011 because the Prefix Digits 9011.

The resulting is 9011441519988776.

That’s magic, the user dials 9011441519988776 then the System Globalizes the dialed digits using the Translation Pattern to obtain +441519988776, the resulting pattern will match our magic Route Pattern \+!, then select the local gateway and the

Transformation Pattern will transform this number to the origin dialed digits so that the call can be routed through PSTN.

Translation Pattern is applied to globalize the number so that the call can be routed internally in the system.

Transformation Pattern is applied to localize the number so that the call can be routed externally in the PSTN.

That’s All!!!


Still the call to 9011441519988776 cannot be routed in the PSTN because the Access Code 9!, the manipulation is simple, if your local Gateway is an H323 gateway, you just use the default digit strip under the dial peer that routes the PSTN Calls! 9T




Published by:

Redouane MEDDANE

Redouane MEDDANE is Cisco Instructor CCSI #35458, 3xCCNP Collaboration, Security and Enterprise and he a published author of some of the most important OSPF Protocol, Security and Collaboration books in the world titled OSPF Demystified With RFC, Network Security All-in-one, and Dial Plan and Call Routing Demystified on CUCM. He is also a blogger at and writes articles about collaboration and security to demystify the most complex topics. His books are known for their technical depth and accuracy especially the OSPF Demystified With RFC book, which is considered as the best OSPF book in the world and named "One of the best OSPF ebooks of all time" by BookAuthority It gives you a hint at the ability to explain complex topics with remarkable ease. He worked as a Cisco Instructor and consultant indifferent Cisco Learning Partner and awarded twice as Cisco Distinguished Instructor Award and Cisco Security Instructor Excellence Award on 2018 and 2019, and Cisco Collaboration Instructor Excellence Award on 2020. The Distinguished Instructor Award recognizes the top 5% of Cisco's most influential CCSI's who provide the highest quality training experience and demonstrate the best overall instructor performance across multiple Cisco technologie and Instructor Excellence Award recognizes the top 25% of elite CCSIs being recognized for delivering top quality training and maintaining high customer satisfaction in their field of expertise.

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