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Cisco employees are moving towards a mobile collaborative office environment – within the workplace. We sit where we like and log into the nearest phone, using extension mobility. But when we traveled to different Cisco offices around the world, we couldn’t log in to the Cisco IP phone:  extension mobility only worked at certain limited locations within our home region.

Now, employee phones can essentially follow them to any Cisco office worldwide because Cisco IT deployed the Extension Mobility Cross Cluster (EMCC) feature on Cisco Unified Communications Manager (Cisco UCM).

With EMCC, an employee who usually works in California (served by the San Jose UCM cluster) can go to a sales office in London (served by the Amsterdam UCM) and use any Cisco IP phone there, as if it was his or her office phone in San Jose. Behind the scenes, the EMCC feature operates in the Cisco UCM software, version 8 or higher.

It sounds simple, but every UCM cluster must now know about all of the other clusters in order to transfer the user’s calls and extension mobility profile correctly. When a user logs-in on a phone that’s assigned to a different cluster, the visiting cluster (in our example, Amsterdam) will broadcast to find the user’s home cluster (San Jose), which will authenticate the user and return the user’s profile and phone configuration. The Amsterdam cluster then configures the guest phone with the user’s information and the employee can start receiving all their own calls, use their own speed-dial keys, just as if they were back home. When a Californian dials the emergency “9.999” number in London, the system routes the call to the local PSTN using the local route group settings.

The EMCC capability is enabled in more than 20 UCM clusters (including ACE environment) and over 110,000 phones have been configured with global extension mobility to be available to more than 57,0000 subscribers. Since the announcement of the EMCC capability in the fall of 2012 we have seen the subscriber base increase by approximately 20% every quarter. Because of the large number of UCM clusters in the Cisco network, the planning, implementation, testing, and operations handoff was scheduled over the course of a few months before EMCC was completely deployed in Cisco.

Cisco IT had another layer of complexity to consider in deploying EMCC: the parallel but separate Cisco UCM clusters in our internal ACE service introduction network. Many Cisco salespeople are users on the ACE network instead of the production network because ACE supports the latest Cisco products for both testing and sales demonstration purposes. We have developed a process for extension mobility cross cluster to continue to work when ACE or production UCM clusters undergo any changes and to ensure that both environments are always kept in-sync.

In addition to implementing the EMCC features on all the clusters, each user must have an extension mobility profile. Today, the Cisco IT helpdesk creates this profile when requested by an employee. In the future, we expect to develop an automated process for profile creation.

However, we expect fewer calls to our helpdesk about extension mobility, because many in the past were from users who didn’t realize that the feature was previously limited only to phones within the same cluster. Now, the EMCC feature will allow our employees to easily stay in touch by phone whenever they are working in another Cisco office, anywhere in the world.

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3 Comments.


  1. Works great as we deployed it 2 months back for 60+ locations and 4 clusters worldwide. However some flexibility over time is required.

       0 likes

  2. Riyas Vallikode

    I have a proposal with a dual mode idea. Cisco has a somewhat same idea. If anyone can contact me I can provide an abstract on this, it just needs our same infrastructure and then a Service Provider’s assistance.

    riyasvallikode@hotmail.com
    09446976332

       0 likes

    • By Dual mode you mean local breakout of calls to PSTN with EMCC instead of. From the person’s home office?

         0 likes

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