ipfw command not working

[Fondjo Bertrand-BFONDJO1]

Hello Folks,
When I try to use the ipfw command to configure a pipe for example: " ipfw add pipe 1 icmp from any to any", 
I am getting this error: "getsockopt(IP_FW_ADD) : Protocol not available". 
Can somebody help with this, please? I can't configure a pipe either. It seems a I am missing something in my free bsd. I am using free bsd 5.2.
 
Please help.
 
Bertrand Fondjo