Hi, There's a problem on the Mac OS X with installed Parallels, which adds virtual nics to the host machine. pjsua-lib bounds to one of these addresses and tries to use it in signalling and media. I know I can use bound_addr explicitly, but it's not the point. I'd like to predict the way my app bounds to the local addresses and do something to make it more convinient for the user. So, is there any algorithm? Here is the user's ifconfig output. The wi-fi interface is en1 with 192.168.1.34; en2 and en3 with 10.211.55.2 and 10.37.129.2 respectively are virtual nics created by Parallels. en1: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500 inet6 fe80::21e:c2ff:febb:c8fc%en1 prefixlen 64 scopeid 0x6 inet 192.168.1.34 netmask 0xffffff00 broadcast 192.168.1.255 ether 00:1e:c2:bb:c8:fc media: autoselect status: active supported media: autoselect en2: flags=8963<UP,BROADCAST,SMART,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 1500 inet6 fe80::21c:42ff:fe00:8%en2 prefixlen 64 scopeid 0x7 inet 10.211.55.2 netmask 0xffffff00 broadcast 10.211.55.255 ether 00:1c:42:00:00:08 media: autoselect status: active supported media: autoselect en3: flags=8963<UP,BROADCAST,SMART,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 1500 inet6 fe80::21c:42ff:fe00:9%en3 prefixlen 64 scopeid 0x8 inet 10.37.129.2 netmask 0xffffff00 broadcast 10.37.129.255 ether 00:1c:42:00:00:09 media: autoselect status: active supported media: autoselect And from pjsua logs: 18:26:37.353 udp0x885800 SIP UDP transport started, published address is 10.211.55.2:49171 And I can't reproduce the problem on my machine -- pjsua-lib still bounds to the proper addres. Alexei