Hi There,
I would recommend following the link below for more details on how to use x25tool. I do believe that there is no simulator provided for X25.
http://docs.sun.com:80/ab2/coll.510.1/X25MANAGE/@Ab2PageView/1122?DwebQuery=x25 tool&oqt=x25tool&Ab2Lang=C&Ab2Enc=iso-8859-1
Good luck.
Thanks
Sujeet (Sun-DTS)