[ns] what is this error "segmentation fault (core dumped)"

[soheila rahmani]

Hi friends
i write a wireless network with 6node. i have an error
"segmentation fault (core dumped)"
if i reduce distance betwen node 5 and 6 this error dosen't show but i saw
in nam,  packets send from node 4 to 6 and dosen't send to node 5!! why ?

my topoloy :
 node1------node2----- node3-----node4------node5-------node6