I use the PTY serial interface on DIrewolf to tie it into Linux's native AX.25 stack. On the Xastir side, I use the native Linux AX.25 stack. I have that all covered here: http://www.trinityos.com/HAM/CentosDigitalModes/hampacketizing-centos.html#19b4.xastir-running --David KI6ZHD