资料来源 : Free On-Line Dictionary of Computing

constant mapping
     
        Some TCP software constructs the destination Ethernet address
        from the top 24 bits of the Ethernet address followed by the
        low 24 bits of the (class A) destination Internet address.
        For this scheme the top 24 bits of the Ethernet address must
        be the same on all hosts on the net.  Contrast {ARP}.