Disable adding Audio calls to C40

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Sep 8th, 2013
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I have an unusual request and I'm struggling to figure it out.

We have several C40's at the office and I want to be able to setup certain devices, or certain calls to deny users the ability to add others to the call locally.

This is especially an issue when an audio caller is added accidentaly.

Is there a way to block the user from adding/dialing another person on a C40 itself during a call?

We have a MCU, a CUCM 9x, and primarily use SIP. I could configure the C40 in multisite or multiway, I just need to enforce a 1:1 call and ensure no one on either end can add an additional user, or at a minimum can not add audio calls.

I'm willing to go in to the backend configuration to do this, but TAC is lacking in help since they consider such capability an enhancement, so I need to get creative.

Any advice would be appreciated.


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Overall Rating: 5 (2 ratings)
irachamiracham Sun, 09/08/2013 - 11:05
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Would this not be an issue with a C20? They do not support multisite features.

If I had a C20 would they not be capable of adding an audio call?

Other options I'm debating:

Enable an outgoing SIP proxy that goes no where, so only incoming requests are recieved.

De-registering is from the Call Manager, so voice traffic has no where to go.

Essentially I'm willing to entertain the concept of 'no outgoing calls at all' if that solves the problem.

Jens Didriksen Sun, 09/08/2013 - 16:24
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C20 (now EOS/EOL), despite not having multisite capabilities, still supports one audio call in addition to the one video call.

Only thing you can currently do on C40 etc is to turn off multisite and also deny incoming multisite calls.

I've seen the same issue raised in the past, and Cisco response has so far been "contact your Cisco rep and submit a feature request".

I believe this additional audio call, at least for the C20, was introduced in TC4.x, so downgrading to TC3.13 could be an alternative solution - I would assume this would the same for C40 as well, but you would have to check the release notes from back then.

However, downgrading from T.6.x will not be that straight forward, most probably not a viable option either, so looks like the "other options" you are debating will be your best solution -  at least for now.


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irachamiracham Sun, 09/08/2013 - 20:00
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Thanks Jen,

What do you think are the best options for disabling outgoing calls? Search rules?

I'm struggling with finding the best option to disable outgoing calls entirely, preferably one that can be quickly restored in the config of the unit (or on the MCU).

Jens Didriksen Sun, 09/08/2013 - 23:52
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Would you be able to do this by a call policy perhaps?

Can't give you an example, but maybe one of the CUCM gurus around here can?


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thobonho Mon, 09/09/2013 - 01:12
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Have you tried to disable Multipoint mode?

xConfiguration Conference [1..1] Multipoint Mode

Define how the video system handles multiparty video conferences.

If registered to a Cisco TelePresence Video Communication Server (VCS), the video system can either use its own built-in MultiSite feature, or it can rely on the MultiWay network solution. MultiWay requires that the video network includes a multipoint control unit (MCU).

If registered to a Cisco Unified Communications Manager (CUCM) version 8.6.2 or newer, the video system can use either the CUCM conference bridge, or the video system's own built-in MultiSite feature. Which one to use is set-up by CUCM.

Both Multiway and the CUCM conference bridge allows you to set up conferences with many participants. The MultiSite feature allows up to four participants (yourself included) plus one additional audio call.

Note that the MultiSite feature is optional and may not be available on all video systems.

Requires user role: ADMIN
Value space:

Auto: If a MultiWay address is specified in the NetworkServices MultiWay Address setting, MultiWay takes priority over MultiSite. If neither MultiWay nor MultiSite is available, the Multipoint Mode is set to Off automatically.

Off: Multiparty conferences are not allowed.
MultiSite: Multiparty conferences are set up using MultiSite. If MultiSite is chosen when the MultiSite

feature is not available, the Multipoint Mode will be set to Off.

MultiWay: Multiparty conferences are set up using MultiWay. The Multipoint Mode will be set to Off automatically if the MultiWay service is unavailable, for example if a server address is not specified in the NetworkServices MultiWay Address setting.

CUCMMediaResourceGroupList: Multiparty conferences (ad hoc conferences) are hosted by the CUCM configured conference bridge. This setting is provisioned by CUCM in a CUCM environment and should never be set manually by the user.

Example: xConfiguration Conference 1 Multipoint Mode: Auto

Jens Didriksen Mon, 09/09/2013 - 01:59
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Even with multisite disabled (multipoint mode off), you can still make a second call which will connect as audio only - that's the problem. This also is, by the way, how C-series without Mulitsite option key installed, behave. It's a "feature".


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William Hurd Thu, 06/19/2014 - 08:47
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I have two (rather high-profile) endpoints where this is continually an issue. 

Could the bridge or call policy disallow multiple calls from a single system? Can audio calls originating from the system be disabled entirely? 

Patrick Sparkman Thu, 06/19/2014 - 12:46
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Hello William -

I don't think it's possible to use CPL to not allow the audio only call.  Simply because the codec will always accept that second call, and only use audio for it.  As long as the audio only call is available the codec won't respond busy, and accept the call, there is no way for the CPL to know.

As Jens has stated, this is a "feature", and to my knowledge, there is no way to disable the audio only call of the codec.

We all who manage video conference systems feel your pain, when a codec manages to call into a bridge a second time creating a loop, or into another codec.


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