Showing results for 
Search instead for 
Did you mean: 
Geo Gon

PVDM3-16 Cisco 2901 DSP VIC2-2BRI-NT/TE "cannot complete conference"


Hi all, 


I have a Cisco Router 2901 with:


1 x PVDM3-16 

3 x ISND2 BRI lines

6 x 7970 IP Phones

When I try to use the built in bridge on the 7970s, I get the message "cannot complete conference"

Now, I have configured a dspfarm for conferencing and it only gives me 2 available sessions:

dspfarm profile 1 conference  
 codec g729br8
 codec g729r8
 codec g729abr8
 codec g729ar8
 codec g711alaw
 codec g711ulaw
 maximum sessions 2
 associate application SCCP


Why do I only have 2 sessions available if I have a PVDM3-16 module?

Why isn't the inbuilt bridge working for conferences up to 3 participants?


Thanks in advance.







Jaime Valencia
Hall of Fame Cisco Employee

You have the smallest PVDM3 there is, that's all it can do when you want high complexity codecs.

Even with just G.711 in the dspfarm config, you can't go past 8, assuming you're not already using resources for TDM

The BIB is NOT used for conferences, unless you use barge.

Is all the config related to conferencing in place?? MRG? MRGL?? is the CFB registered??

What have you checked???




if this helps, please rate

Hi Jaime, thanks for the answer. 

How many channels my 3 BRI isdn lines are taking off the PVDM? 

The dspfarm, event though only has 2 sessions, is up and registered. 

What do you mean by using resources for TDM.


Many thanks again.

James Hawkins

Are you using CUCM or CUCM Express?

If the latter you can use the BiB for 3 party conferencing. If the former then you can do it in software on the CUCM servers (limited to G711 codec) or on a router with PVDM.

If you remove the g729 codecs from your config you will get support for more sessions but I guess that you need them or you would be doing software conferencing?


Hi James, thanks for the reply. 

I'm using CME.

All I have here is a small office with 10 phones and we are using g711. Do I even need g729 under the my codec profile?


The only codec you need for a single site is g711ulaw.

If you only want to support three parties per conference then no specific configuration should be needed as CME will do this by default.

If you want to support more than three parties you will need to use PVDM resources.

The link below may help.

One last thing - these software conferences are hosted by the router CPU rather than the BiB.



Hi James, 

The only reason I was configuring dspfarms is because the native conference on CME was not working. I was also getting  "cannot complete conference"

Content for Community-Ad

Spotlight Awards 2021