No voice between remote extensions

I installed Asterisk All of the extensions loged on to the PBX, remote extension included. The conversation between two local softphones is flowing without any problem,I have calls over telephone line without difficulties too,but conversation between two remote-one of them is local- softphones is not succefull - no voice in both. The ports 5060 , 5000-30000 are opened in D-Link DI-524 router for my Asterisk Server in TCP/UDP.
I understand,that it is ports or codec issue,but I don’t now how to resolve it. I need your help.
Thanks fo advice,