Hi all, Can't receive a 500 (Server Internal Error) response from openser register server when sending a REGISTER with the equal CSeq header field value to the last value of CSeq or lower than the number and “*” in a Contact header field. The details can be as follows: 1 Test topology: NUT(REG && PX) UA11 UA12 DNS | | | | IP : 3ffe:501:ffff:50::50 3ffe:501:ffff:1::1 3ffe:501:ffff:2::2 3ffe:501:ffff:4::1 aor-uri : ss.under.test.com UA11(a)under.test.com UA12(a)under.test.com contact-uri : UA11(a)node.under.test.com UA12(a)node11.under.test.com 2 tcpdump file can be seen in "12 SIP Registrar- Record-Route header field in REGISTER request" attachment 3 openser configuration file can be seen in "openser.cfg" attachment How can I modify the configuration file if I want to receive the 500? -------------------------------------- Regards! Hu xiaoqiang