Calls dropping with error “SIP/2.0 487" Request Terminated” after successful connections. In order to support fast failover, there is a setting in
Lync called “enable outbound routing failover timer”. This trunk setting
requires that the SIP trunk notifies Lync within 10 seconds that it is processing
an outbound call. This setting can and
does cause problems on networks where latency delays the response time or the
gateway takes longer than 10 seconds to respond. Some SIP trunks will either
not provide this notification, or is not able to get it back to the Lync server
within 10 seconds. In this case the call will drop in about 10 seconds and a
“SIP/2.0 487 Request Terminated” will appear in the Lync server SIP transaction
logs.
To resolve this issue uncheck the box “Enable outbound
routing failover timer”. This setting is located at LSCP>Voice
Routing>Trunk Configuration
