/mcpC H A P T E R 34 Extension Mobility Roaming Across Clusters To deploy Extension Mobility Roaming Across Clusters, you must be running a minimum release of Cisco Unified Communications Manager 12.0(1)SU1. Note • Extension Mobility Roaming Across Clusters Overview, on page 453 • System Requirements for Extension Mobility Roaming Across Clusters, on page 454 • Extension Mobility Roaming Across Clusters Login, on page 454 • ILS Interaction, on page 457 • Extension Mobility Roaming Across Clusters Task Flow, on page 457 • Extension Mobility Roaming Across Clusters Interactions and Restrictions, on page 462 • Different Types of Extension Mobility, on page 462 • Extension Mobility Roaming Across Clusters Troubleshooting, on page 463 Extension Mobility Roaming Across Clusters Overview Extension Mobility Roaming Across Clusters gives users the ability to roam across multiple cluster and make or receive calls even when the user's home cluster is down. This feature leverages the Intercluster Lookup Service (ILS) to replicate Extension Mobility users' directory numbers across all the clusters. When a user logs in to a roaming cluster, their phone registers to the roaming cluster using the directory number. Unlike Extension Mobility Cross Cluster (EMCC), where the phone from the visiting cluster registers to the home cluster, the roaming feature allows the user to maintain their registration in whichever cluster they are visiting. Configuration Overview To deploy this feature, you must do the following: • Set up an ILS network—ILS is used to synchronize directory number across the clusters. For details on configuring ILS, see the Configure Intercluster Lookup Service chapter in the System Configuration Guide for Cisco Unified Communications Manager. • Set up a uniform dial plan—you require a uniform dial plan across the ILS network. To set up a dial plan, see Configure the Dial Plan chapter in the System Configuration Guide for Cisco Unified Communications Manager. Feature Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs 453