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CUCM 7.1.5 SIP trunk issues with VCS X7.1

jarrod sousa

hello all, i have now encountered this issue 2x in 2 seperate customer environments.  the promlem i am having is getting video to pass between CUCM and VCS when CUCM is on version 7.1.5.  i have built a sip trunk according to the Cisco config guide (doc # D14602.09).  right now if i place the call from the C40 as H323 to the 8941 i get video and audio both ways.  if i reverse the same call flow i get audio only.  if i place a SIP call i get signaling only (no audio/video).  this works like a champ on CUCM 8.  what am i missing here?  i have SRTP, and retry video as audio boxes checked and MTP disabled.  i have set the max per call bandwidth on the VCS to 384k for calls to/from CUCM.  i have tried using the CCM built in MTP and i get audio only at that point.  what could i possibly be missing?

Good call flow: C40 (h.323 protocol running TC4.1.x )-> VCSC (X7.1) -> SIP Trunk -> CUCM (7.1.5) -> 8941 IP phone

everything else fails

7 Replies 7

Patrick Pettit
Cisco Employee
Cisco Employee

HI Jarrod.  Could be a possibilty of things here.  The reason why it may work from C40 (h323) to 8941 (SIP) may be because of the interworking function.  Since VCS doesn't know the capabilities on the h323 when sending INVITE to CUCM, the INVITE is empty, so in essence, when the 200 ok comes from CUCM, the VCS has to send its TCS to the C40. C40 sends TCS and then VCS returns ACK with SDP to CUCM with its capabilties. 

I'd be a bit curious to see a trace from the VCS Side showing a failing call from 8941 to C40 generating audio only.  Maybe something in the SDP the 8941 doesn't like perhaps?  CUCM trace would be interesting to see here also. 

There have been significant improvements made with CUCM 8, 8.5, 8.6.2 along the way with regards to content sharing over SIP (BFCP) support etc to allow content sharing between the two.  If you wish to take advantage of these,  improvements, upgrading the CUCM to 8.5 or higher may be best to suit your needs. 



Patrick, thanks for your reply.  1st off i get that upgrading to 8.x is the reccomendation and i have already fought that fight.  the issue is that both customers have UCCE/UCCX in their environment and we cant upgrade easily.  that being said i have been unable to find anything that states CUCM 7.1.5 wont support video between VCS and CUCM.

I did some more testing and need to revise my details form above:

C40 (h323) -> VCS -> CUCM -> 9971 = audio and video both ways

9971 -> CUCM -> VCS -> C40 (h323) = audio only

C40 (h323) -> VCS -> CUCM -> 8941 = audio and video both ways

8941 -> CUCM -> VCS -> C40 (h323) = audio both ways and video from 8941 to C40 only

C40 (SIP) -> VCS -> CUCM -> 9971 = audio only

C40 (SIP) -> VCS -> CUCM -> 8941 = audio and video both ways

E20 (SIP) -> VCS -> CUCM -> 9971 = audio only

9971 -> CUCM -> VCS -> E20 = no connect.  E20 rings but when answers, call disconnects

E20 (SIP) -> VCS -> CUCM -> 8941 = audio and video both ways

8941 -> CUCM -> VCS -> E20 = no connect.  E20 rings but when answers, call disconnects

E20 -> VCS -> CUCM -> 7940 w/CUVA = audio and video both ways

7940 w/CUVA -> CUCM -> VCS -> E20 = no connect.  E20 rings but when answers, call disconnects

Software verisons:

VCS - X7.1

CUCM - 7.1.5

C40 - TC5.1.2

E20 - TE4.1.1

9971 - sip9971.9-2-4-19

8941 - sccp9-1-2-00

It is interesting to see this post.

The comment made by Patrick with regards to Empty invite is the main reason which always creates confusion when it comes to Interworking.


In your test you will observe that if the end point registered to VCS are using SIP, the call both way will work in most cases.

When the H323 device comes into play, then it creates many issue and mostly in the initial invite CUCM is not aware of the VCS registered end device capability. That's why the CUCM 8.x has this option of using "Normalization script" at the SIP trunk level and later they fixed it in CUCM 8.6 version.

I will also say look for :

- MRGL ( when it comes to H323 and SIP- there exist a dtmf mismatch so you can use an MTP in passthrough mode )

- Region relationship and as part of the device pool select some media resource .

I am still facing issue with the 9971 Phones but it may be one off.

If you are planning to go for 8.x then at least start with 8.6 version.

Yes, capture at the CUCM and VCS level will help you out more.


thank you so much for the clarification on the difference between CUCM 7 and 8!  i have asked dozens of Cisco engineers and no one had an answer.  that makes total sense in why it has issues.  as a work around i built a H323 trunk between VCS and CUCM and it seems to work fine.  i am just having some issues with 8941 phones but everything seems to be working.  i will update again later on if i can get all issues resolved.

OK  found the issue with the 8941.  it was a shared line with another device in CUCM.  gave it it's own line and works great.

to summarize CUCM 7.1.5 and VCS video calls require H323 trunk, not SIP.

It just dawned on me my vernacular may not be correct for the CUCM purists

Technically did not configure a H323 trunk in CUCM to the VCS, we built the VCSC as a H323 Gateway in CUCM.  I am very sorry if i tripped anyone up.

thanks that my response helped you.

Pl rate if possible.


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