problem in kernel compiling with netgraph option

[niraj kumar]

when i add these line in  my  kernel file
options NETGRAPH
options NETGRAPH_ETHER
options NETGRAPH_SOCKET
 
after using ngctl show i see ed0 as ethernet node but when i attempt to insert a tee node between lower and upper hook y using 
         ngctl mkpeer ed0: tee lower right
i am facing this problem 
   module-register : module netgraph already exist
linker_file_sysinit  "netgraph.ko"  failed to register

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