The default extension range assignment is:
User Extensions: 1000-6299
User Extensions is referring to the extensions created under Web
GUIExtension/TrunkExtensions page.
Pick Extensions: 4000-4999
This refers to the extensions that can be manually picked from end
device when being provisioned by the UCM6510. There are two related
options in zero config pageAuto Provision Settings, "Pick Extension
Segment" and "Enable Pick Extension". If "Enable Pick Extension"
under zero config settings is selected, the extension list defined in "Pick
Extension Segment" will be sent out to the device after receiving the
device's request. This "Pick Extension Segment" should be a subset of
the "Pick Extensions" range here. This feature is for the GXP series
phones that support selecting extension to be provisioned via phone's
LCD.
Auto Provision Extensions: 5000-6299
This sets the range for "Zero Config Extension Segment" which is the
extensions can be assigned on the UCM6510 to provision the end
device.
Conference Extensions: 6300-6399
Ring Group Extensions: 6400-6499
Queue Extensions: 6500-6599
Voicemail Group Extensions: 6600-6699
IVR Extensions: 7000-7100
Dial By Name Extensions: 7101-7199
Fax Extensions: 7200-8200