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New Member

xfer of external call, one way audio

We have a CUCM in our North American office, and a CUBE in our German office. Recently (after using the system for 4 months) I have been informed inbound calls lose outbound audio when they are transferred at our German office.

I've mapped out the topology and call flow as I understand it, perhaps someone can point out where we could be losing the media stream. Also my understanding of the exact signalling/media flow is probably incorrect, please feel free to correct me.

Call route:

(1) - call is coming in from the PSTN

(2) - CUBE signals CUCM as to call destination (via VPN)

(3) - CUCM translates DID to German extension, signals CUBE (via VPN) to make media connection with Ext 402

(4) - Ext 402 rings, picks up call

(5) - Ext 402 wants to transfer call to Ext 401, signals CUCM (via VPN)

(6) - CUCM signals CUBE (via VPN) to ring 401

(7) - Ext 401 rings, and user picks up call

At this point the user on Extension 401 can hear the other end, but audio is not making it back out the trunk. Typically I would assume a NAT issue here, but seeing as the media stream is already on the local LAN in Germany it seems to preclude NAT'ing issues.

Any help is much appreciated.



xfer of external call, one way audio

Will you be able to post relevant CUBE configurations here? Are extensions 401 and 402 in the same Vlan? Also a "show call active voice brief" and "debug ccsip messages" for a failed call would also help.

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New Member

Re: xfer of external call, one way audio

Hi George,

In Germany all the 4xx extensions are in the same vlan. The scenario outlined above was tested with exclusively German extensions.

For testing I've used two phones on our local phone subnet in NA, but its only on xfer that audio is lost. I can make outbound calls from a 4xx extension in NA using european device pool/dial patterns without issue.

When I run through a test here in NA, the extension answering the forward gets background noise only, the inbound caller never comes off hold music after they are xfer'd.

In the attached logs the initial call comes from 452 to external number 022145580030 which is translated to and answered by 450. 450 then attempts to xfer the call to 238 (NA device pool) and gets no audio, while 452 hears hold music even after being xfer'd.


debug ccsip:

show call active..:


xfer of external call, one way audio

Oh ok, could you make sure there are no SIP inspection commands on the devices that do the site-to-site tunnel?

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New Member

xfer of external call, one way audio

If you're referring to firewalls, there currently are no rules on the tunnel.

Likely related: the German office cannot connect conference calls with external numbers. The first call works as expected, but when the second external number is called and the two calls are merged into conference, both external endpoints only hear busy music.

I've attached the voip ccapi debug if there's anything useful in it.

This call is with 452 calling external number 15195132407 then an extension, then attempting to conference in another another extension at the same external number.

Appreciate any help.

New Member

xfer of external call, one way audio

Solved this issue.

I had:

voice service voip


  midcall-signaling passthru

Changed to

  midcall-signaling passthru media-change

Solved issue with both xfers and with conference calls.

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