Hi team,

This is a Lync 2010 environment. Federation is done with 7 orgs. 6 of them are working fine. however, with one federated partner, we are having issues with audio/video calls. when ever a call is made, it's getting dropped and the below error is generated from client end.

SIP/2.0 481 Call Leg/Transaction Does Not Exist

Ms-client-diagnostics: 52085;reason="Dialog does not exist"
Proxy-Authorization: TLS-DSK qop="auth", realm="SIP Communications Service", opaque="5BB4331A", targetname="<FrontEndFQDN>", crand="0594e527", cnum="25", response="ba0cbdf773f7bdc6725d9b689e9eaf75cb6c6bd2"

I'm wondering why calls are failing with this account only.

Thank you.
Chris.

If all other federation works fine, I wolud think it is a configuration problem on the other edge server. Maybe some ports are not allowed through the firewall for A/V

Hi,

As the issue only happen with one federation partner, it maybe the issue on the partner side. Please contact partner to check if they have the issue only with yours or also with other federation partners'.

Best Regards,
Eason Huang

Hi Holger, 

Yes, all other partners are good. I'll look into this and update.

Thank you.
Chris.