どのマシンと言いますと？
FreeBSD4.8のローカル側につないだWindowsからです
インターネット側のインターフェースに上のような設定をして

pass out on xl0 all head 200

block out from 127.0.0.0/8 to any group 200
block out from any to 127.0.0.0/8 group 200
block out from any to 1.2.3.4/32 group 200
block out from any to 10.0.0.0/8 group 200
block out from any to 172.16.0.0/12 group 200
block out from any to 192.168.0.0/16 group 200
block out from any to 0.0.0.0/8 group 200
block out from any to 169.254.0.0/16 group 200
block out from any to 192.0.2.0/24 group 200
block out from any to 224.0.0.0/4 group 200
block out from any to 240.0.0.0/4 group 200
block out from any port 136 >< 140 to any group 200
block out from any to any port 136 >< 140 group 200

#pass out proto tcp all flags A/A group 200
#pass out from any to any port = 53 group 200
#pass out proto tcp all flags S/SA group 200
#pass out proto udp from any to any port = 123 group 200
block out proto icmp all group 200
#pass out proto icmp all icmp-type 8 group 200

でも　WindowsからゲートウエイにしたこのFreeBSDを通過して外部へ
どんなアクセスも出来ます。