A.255.255.255.0 B.255.255.255.128 C.255.255.255.192 D.255.255.255.224
A.中繼器 B.路由器 C.網橋 D.網關
A.10.10.10.1 B.255.255.255.0 C.127.0.0.1 D.192.0.0.1