This might be helpful but it's a bit over my head... Can someone have a look ?
http://www.linuxjournal.com/article/9399?page=0,0
edit: my SIP Passthrough is enabled in WAN in the GUI but somehow I don't see anything related to 5060 in iptables-save ???
http://www.linuxjournal.com/article/9399?page=0,0
edit: my SIP Passthrough is enabled in WAN in the GUI but somehow I don't see anything related to 5060 in iptables-save ???