In my day job, I support a company that has extension mobility configured across many locations. We see a variety of problems that occur - mostly from misconfiguration (we didn't install it

). The following step-by-step guide is a great checklist if you're unsure about an existing extension mobility configuration, or if you are planning to install extension mobility for the first time.
Verify Extension Mobility Service is RunningNote: I've also seen where multiple call managers are being used to register phones, however, the Cisco Extension Mobility Service is not active on all servers. Watch out for this.
From the Navigation menu select Cisco Unified CallManager Serviceability
Select Tools > Control Center – Feature Services
Make sure that the Cisco Extension Mobility service shows status Activated
Configure Extension Mobility ServiceFrom the Navigation menu select Cisco Unified CallManager Administration
Select Device > Device Settings > Phone Services
Click Add New
In the Service Name field, type Extension Mobility
In the Service Description field, type Login and logout service
In the Service URL field, Enter the following URL:
http://:8080/emapp/EMAppServlet?device=#DEVICENAME#Click Save
Modify Enterprise Parameters to Reflect IP Address of CallManagerSelect System > Enterprise Parameters
Under Phone URL parameters, change all fields from CCMNAME:8080 to IPADDR:8080. Change ONLY your existing server name to the correct IP address.
Click Save
Click Ok from the pop-up warning.
Click Reset
In the pop-up window select Reset
Click Close
Create a Device Profile Default for Each Phone Model (using Cisco Extension Mobility)Select Device > Device Settings > Default Device Profile
From the drop down list, select the phone model to be configured, for example, Cisco 7960.
Under Description, enter a description of this profile.
Under Phone Button Template, select Standard 7960 SCCP.
Click Save
Repeat for each model phone to be configured
Create Device User Profile for a UserChoose Device > Device Settings > Device Profile and click Add New.
From the drop down list, select the phone model to be configured, for example, Cisco 7960
Click Next
Enter a Device Profile Name, for example “Your Name” .
From the Phone Button Template field, select Standard 7960 SCCP.
Click Save.
On the left hand side of the screen, click the link Line [1] – Add a new DN.
Choose a valid DN from your internal dialing plan for the location, enter that DN in the Directory Number field.
Under Route Partition, select your city’s Headquarters Partition.
Under Directory Number Settings choose a CSS of appropriate access.
Enter any Call Forward and Call Pickup Settings as necessary.
In the Display (Internal Caller ID), enter the User’s name.
Click Save.
From the Related Links: menu, select Subscribe/Unsubscribe Services.
In the Select a Service, select Extension Mobility, then click Next.
Click Subscribe.
Click Save.
Repeat for any additional lines.
Associate User Device Profile to a UserFrom the menu, select User Management > End User.
Click Find
Select the user from the list that matches the profile that was created.
Under Extension Mobility > Available Profiles, select the profile and move it to the Controlled Profiles selection.
Under Default Profile, select the profile.
Click Save.
Configure and Subscribe Cisco Unified Ip Phones to Service and EnableSelect Device > Phone from the menu.
Select the phone from the list of devices.
In the Related Links: field, select Subscribe/Unsubscribe Services and click Go
In the pop-up window, under Service Information, in the Select a Service pull down menu, select Extension Mobility.
Click Next
Click Subscribe
Click Save
Close the pop-up window.
Under Extension Information, check the Enable Extension Mobility box.
Under the Logout Profile field, select – Use Current Device Settings –
Click Save.
Click Ok from the pop-up warning.
Click Reset
In the pop-up window select Reset.
Click Close.
Thank Ref : http://www.voicecerts.com/2010/06/step-by-step-guide-to-configuring.htmlPhotos by Phuket IT : https://plus.google.com/u/3/photos/111464961497410951609/albums/6032397364284267089?hl=th