Configuring DDI's with Grandstreams UCM6100 Series PBX and 2Talk

Scenario:
With Grandstream Networks UCM6100 Series IP/PBX you can configure Outbound DOD's (DDI's). An example of why you would use this might be that you wish to only register 6 trunks on your UCM and then have 30 DDI numbers each assigned to extensions on the UCM. Each extension on the PBX when dialling outbound will use on of the 6 available trunks and present its own configured DDI number as the caller id instead of the trunks caller id.

Products Used:
Grandstream UCM6100 IP/PBX
Grandstream GXP2160 6 Line HD IP Phone
Grandstream GXP2170 12 Line HD IP Phone

Step 1:
Login to your 2Talk Pilot account (main trunk) and navigate to Outbound Calls > MyCLI - Call Privacy and Caller ID
Select the type of Caller ID: Present a 2talk phone number (default)
2talk phone number selection: Default Caller ID

Step 2 - Creating a SIP Trunk:
Login to your UCM6100 IP/PBX and navigate to PBX > VoIP Trunks > Create New SIP Trunk
Provider Name: trunk_1
Host Name: sip.2talk.co.nz
Keep Original CID: disable
Keep Trunk CID: disable
Username: 2talk_trunk_number
Password: 2talk_password

Step 3 - Configure SIP Trunk:
Edit the VoIP trunk you have just created and amend the following:
From Domain: 2talk.co.nz
From User: 2talk_trunk_number
Send PAI Header: enable

Step 4 - Create SIP Extension 1001:
Navigate to PBX > Basic/Call Routes > Extensions > Create New SIP Extension
Extension: 1001
CallerID Number: DDI_number_1 (i.e. 2talk DDI number to map to this extension)

Step 5 - Create SIP Extension 1002:
Navigate to PBX > Basic/Call Routes > Extensions > Create New SIP Extension
Extension: 1002
CallerID Number: DDI_number_2 (i.e. 2talk DDI number to map to this extension)

Step 6 - Configure Extension 1001 DDI:
Navigate to PBX > Basic/Call Routes > VoIP Trunks > DOD
DOD Number: DDI_number_1
Selected Extensions: extension_mapped_to_DDI_1

Step 7 - Configure Extension 1002 DDI:
Navigate to PBX > Basic/Call Routes > VoIP Trunks > DOD
DOD Number: DDI_number_2
Selected Extensions: extension_mapped_to_DDI_2

Step 8 - Create Outbound Route:
Navigate to PBX > Basic/Call Routes > Outbound Routes > Create New Outbound Route
Calling Rule Name: LINE01_OUT
Pattern: _X!
Privilege Level: International
Use Trunk: trunk_1

Step 9 - Apply Changes and Testing:
Click Apply Changes in the top right.

You should now be able to make an outbound call from extension 1001 you should see on the receiving phone that the call is originating from DDI_number_1
Likewise when you make an outbound call from extension 1002 you should see on the receiving phone that the call is originating from DDI_number_2