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Conference call to external number

I have a callmanager 11.5 su1. I was wondering how do AD Hoc conference calls restrict outbound calls.

I know there a system parameter to stop offnet calls. Does the confernce call concatenate the device and line CSS or just the device or just the line.

It looks like it is just the device but I am not sure. Any help would be great

Cisco Employee

Re: Conference call to external number

I think the parameter you're referring to, is the transfer external to external, nothing to do with conferencing.

When you place a conference, what allows that call to be placed, is the regular CSS from the device/line, so, you'd need to prevent ALL calls to those numbers, to prevent them from being conferenced in.


It's not that the CFB places the call, it's the device you use to place the call, and then press the conference button that determines whether you can, or cannot, reach your destination.



if this helps, please rate

Re: Conference call to external number

Jamie that was my understanding but here is why I asked. In the old days around 2000 and cucm 3.0.X when the css's got concatenated it was the device that was first to be looked at  so back then we didn't even bother with the line CSS. That changed and I am blurry cucm 3.6 or 4.0 or somewhere there Unless I am wrong and I was right once, there are still some devices today where the device CSS is what matters. SO here is why I aksed

I deployed a hospital and only security and switchboard can call 911. When anyone dials it uses a translation pattern and sends to switchboard and she conferences in 911. The line CSS had the 911 route pattern partition and it was working. Then it stopped well it worked randomly maybe 1 out of 10 calls would work. The issue was you got a intercepy saying the number you have dialed can not be completed as dials, The phone could call call 911 and conference to external worked except 911. My colleague changed the device CSS to one that had the 911 partition in it and now it works 100%. SO that is why I asked. I would have thought the device and line get concatenated as usual so the way it was setup it should have worked.

So I looked to the forum for help. I was trying to understand if the final CSS for conferencing is made up of the device/line in that order or line/device, line or just device.

I hope this all makes sense. I am nervous that this will stop working again.

Thanks for the response


Hall of Fame Master

Re: Conference call to external number

Jaime is 100% correct, there is no way to prevent conferencing external callers yet allow external calls to happen from specific DN.  What would be the reasoning behind it?  If I am a user with permissions to make external calls, why would you need to prevent me to conferencing external calls? Just curious as I have never had such a requirement.


Re: Conference call to external number

Chris thanks for reply , short version I have a phone that is only device allowed to make 911 calls. so all 911 calls go to this phone she conferences in 911. IT was working 90% of the time. The failure was an intercept saying "I am sorry but the number can not be completed as dialed". The 911 pt was in line CSS. it stopped working.

MY colleague put a CSS on the Device that could call 911 and it started working again. 

SO i got thinking back to 2000 and CUCM 3.0.X where the device was first  the the line when it gets concatenated I maybe wrong but there are still a few things that work this way. So like Jamie mentioned it was device/line . so I am really wondering does conference css get made up as the line CSS, Device CSS or both.

I am really concerned that it will come back. The failure by the way was an intercept saying " I am sorry the number you dialed can not be completed as dialed" or close to that.

Hope this all makes sense now,

Thanks for answering Chris

Hall of Fame Master

Re: Conference call to external number

The way CSSes work in CUCM (any version as this has not changed) is different for different device types, for example phones will  concatenate the CSSes and use the DN CSS as more preferred, so if you have 2 identical matches one assigned to PT matched by Device CSS and one by DN CSS, the DN CSS will be used. However, in proser design there should not be identical patterns in 2 different partitions assigned to CSSes for specific site/phone.

If only device or DN CSS is applied then it should work as expected and as long as it has access to the pattern work. Perhaps the change you applied invokes different 911 pattern from different partition.


Re: Conference call to external number

Chris thanks for the information. I am aware of how it all works. I have the 911 as the first entry of the CSS for the line. The device never had 911 in the css, however when this stopped working and my colleague put a ccs on the device that had access to the 911 partitiion and it started working, SO I started wondering how Adhoc conferencing actually works when it comes to CSS  device and line. My concern is it a bug and it will come back.

I don't like when a CSS gets added to a device and both the line and device css have the partition

911 in them.

I do appreciate your help.

On a side note did you do work for a Customer AZGA in the US.?


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