Understanding PPI mode: DOD Number when Call Forward to External Number

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Description

This article explains the P-Preferred-Identity (PPI) Header in UCM’s INVITE message when UCM forwards the call from the extension to an external or mobile number.

Test Steps

  1. Configure a VoIP Trunk
  2. Go to Advanced Setting > enable Send PPI Header and set PPI Mode to ‘DOD Number’
  3. Configure DOD number: ddd9955 and DOD Name: DDD9955 at the Trunk > Advanced Settings
  4. Configure CFU to external number: 9004 on the Extension 8003’s setting
  5. External Number 9005 calls 8003
Figure 1: Step 2 – configure PPI Header and PPI Mode: DOD Number
Figure 2: Step 3 – At the VoIP Trunk > configure DOD number: ddd9955 and DOD Name: DDD9955
Figure 3: The forward’s INVITE to external number 9004 contains PPI header with 9005’s DOD : “ddd9955″sip:ddd9955@192.168.129.74

Packet capture

external9005_callin_cfu_9004.pcap_Download

Outbound CID Priority

TO vs Request Headers

The Request-Line and To headers show the DID used by the PBX, eg. 8887771234 is the DID, it is shown as 8887771234 in the Request-Line but as +18887771234 in the To header. The Request-Line header shows the destination whereas the To header shows a caller name and a logical destination such as a proxy or an intermediate hop.

2 thoughts on “Understanding PPI mode: DOD Number when Call Forward to External Number”

  1. Hiii Shi

    Is it possible to send DOD of extension ( From where call forwarded) to external number when call forward.

    Call comes from 99xxxxxxxx >> Extension 8003 >> Call Forward >> External no 88xxxxxxxx.

    Extension DOD: 120xxx8003

  2. Pingback: way to pass through DODs between two Grandstream IP PBX UCM

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