I'm selling/renting Linksys/Cisco phones with various SIP servers. I have seen the following behaviour with SPA942 and SPA962 when using 6.1.3a fw and conference bridge URL. When the third person is reached and there are two calls on hold, conf soft key is pressed. An INVITE to conf bridge ([email protected]) is sent for a phone which started the conference and two REFERs for other parties are originated. REFERs however have Refer-To header point to the contact (sip:<IP ADDRESS of conf bridge>) and not to the conf bridge URL. I thought this was due to option "Refer-To target contact" being set to "Yes", so I set this option to "No", but same behaviour continued. For SIP servers which are B2BUA and not proxies this behaviour is wrong and not possible to work with, therefore I think this is bug that should be fixed.
I will attach the SIP traces with needed data.