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comfort noise warning at lync


I have integrated my CUCM 8.6 with the microsoft LYNC server for internal calling, which is working fine. But at the LYNC sever, we are getting warning and the warning is :

Log Name:      Lync Server

Source:        LS Mediation Server

Date:          5/1/2012 10:58:32 AM

Event ID:      25073

Task Category: (1030)

Level:         Warning

Keywords:      Classic

User:          N/A



The Mediation Server service has received a call that does not support comfort noise.  This event is throttled after 5 calls from a single Gateway peer.

The Mediation Server service has received a call that does not support comfort noise from the Gateway peer,

Cause: The Gateway peer does not support comfort noise.


Please ensure the comfort noise option on the Gateway has been enabled.

Event Xml:

<Event xmlns="">


    <Provider Name="LS Mediation Server" />

    <EventID Qualifiers="33798">25073</EventID>




    <TimeCreated SystemTime="2012-05-01T05:28:32.000000000Z" />


    <Channel>Lync Server</Channel>


    <Security />





</Event> is my CUCM IP address.

does call manger have any option like that?


Pawan Arora

Everyone's tags (4)
Super Bronze

comfort noise warning at lync

I don't believe so. Cisco gateways and other devices do support comfort noise of course, but it's on by default (

Perhaps have a look at these threads where a similar error was traced to other signalling issues? :

Is it actually causing an issue, or is it just the event being logged?


Aaron Please remember to rate helpful posts to identify useful responses, and mark 'Answered' if appropriate!
New Member

comfort noise warning at lync

Aaron - you are correct on the routers, however, if Pawan is using a Cisco Call Manager as his PSTN in Lync you are incorrect.

Pawan - If you are using a Cisco Call Manager as your PSTN in Lync, in Call Manager, on the SIP trunk profile, in the "Parameters used in phone" section, make sure you have the "Enable DAV" checkbox selected.

This fixed the event id 25073 on our Lync server and we no longer had issues with comfort noise not being generated.

Hope this helps!

- Will

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