The Attendant DN feature is a digit manipulation technique for inbound calls. To understand it, let’s assume we have an analog trunk port such as FXO port on a voice gateway. When the gateway receives a call on the FXO port, the FXO port becomes in the off-hook state and a circuit is closed between the central office and the gateway, like in home phone dialing. A dial tone is played (by the CUCM instead of the central office) and the FXO port is waiting for the user to dial more digits.
At this point comes the Attendant DN feature. The Attendant DN allows to send a set of digits to the call routing component as soon as the analog port goes off-hook. So instead of waiting for additional digits to be dialed, a new batch of digits is dialed (the Attendant DN value) and transmitted to the call routing component.

The Attendant feature is similar to the Prefix Digits where a set of digits is added before the call is transmitted to the call routing component.

Attendant DN configuration

The Attendant DN is configurable on analog ports such as FXO and FXS ports. It is not configurable on digital trunk ports, simply because digital gateway protocols such as MGCP PRI, H323 and SIP trunks use enbloc dialing. So they get the whole dialed number in the inbound call.

Example 1: Attendant DN setting on an analog voice gateway, equipped with a Ground Start FXS port



Example2: Attendant DN setting on an analog voice gateway, equipped with a Loop Start FXO port



cover photo credit: Austrian Airlines ( [CC BY-SA 2.0 (], via Wikimedia Commons

Categories: CCNP Collaboration

Keyboard Banger

Keyboard Banger is a network engineer from Africa. He has been working in network support and administration since 2008. He started writing study notes about certification exams and technology topics a couple of years ago. When he's not writing articles, he can be found wandering on technical forums.


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