Hi all, According to Apple and Google’s app review guideline, all apps need to support IPv6-only network, so I tried to enable ipv6 support on my freeswitch server. In my development environment, a server with both ipv4 and ipv6 address is ready. Server Info: Debian stretch 9.9 FreeSWITCH Version 1.8.7+git~20190702T200609Z~6047ebddfc~64bit (git 6047ebd 2019-07-02 20:06:09Z 64bit) Also, profile external-ipv6 and internal-ipv6 for freeswitch had also enabled. In addition, a pure-ipv6 network(no NAT64) is also ready for test. As the test result, clients could access to server via ipv6-only network for registration(sip package showed in server with siptrack), but failed to make calls in same network. Freeswitch log showed a failure in originate, which returned an 606 USER NOT REGISTERED. Both clients was showed in “show registrations” with correct ipv6 address, but Sofia couldn’t get contact string(got 606 in sofia_contact). Is there any additional settings need for Sofia to enable ipv6 support? Any suggestion would be appreciated. Regards.