Hi Sergey, you nailed it! Thank you for your fast response. If you know where to look it appears simple. But if you have no idea from where the problem comes from ... Best regards, Bernd

Hi Bernd I also use dual-stack. When the destination has an ipv6 and ipv4 address in the DNS, then kamailio should be able to use either of those protocols to reach it. So: CPE => ipv4 => Kamailio => ipv6 => CPE should work, if the involved CPE play along! Example: Cisco SPA112 don't know about IPv6 IP addresses in SIP headers and their parser uses ':' as hostname:port separator completely breaking IPv6 addresses and building broken header in it's replies. Also mind, the RTP stream. And ipv4 only CPE will not be able to exchange RTP with an CPE advertising ipv6. So using ICE might help and maybe even use rtpengine to tank different protocols on each leg. Mit freundlichen Grüssen -Benoît Panizzon- -- I m p r o W a r e A G - Leiter Commerce Kunden ______________________________________________________ Zurlindenstrasse 29 Tel +41 61 826 93 00 CH-4133 Pratteln Fax +41 61 826 93 01 Schweiz Web http://www.imp.ch ______________________________________________________