Some softphone open source is supported in IPv6

Hi there,

I have a IPv6 network in our labrary that is built up with 3 routers, i put one server under the net 2002:0:0::100:0/64, put two another clients under the net 2002:0:0::200:0/64, if i want to achive a call between these two clients, besides i upgrade the asterisk to version 1.8, what configuration else i should do? what softphone could be supported in IPv6?
Any help i could appreciate!!

Best regards

LI Xiao