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【正文】 r B IP Address = Hardware Address = 08004. . . IP Address = Hardware Address = 08009. . . ARP Cache 08009. . . 08006. . . ARP Cache 08004. . . 4 1 08005... 08006... 2 5 ping ARP Cache 3 Network 1 Network 2 3 2 1 ARP Broadcast for Router Interface A ARP Broadcast for Router Interface B A B 4 5 Reverse Address Resolution Protocol (RARP) ? To discover the identity of the IP address for diskless machines with a RARP broadcast ? For diskless workstation asking for its IP address IP Addressing IP Terminology The Hierarchical IP Addressing Scheme Network Addressing Address Class Summary Network addresses: Special Purpose and Guidelines Assigning Network Addresses Assigning Host Addresses IP Addressing was designed to allow a host on one work to municate with a host on a different work, regardless of the type of LANs the host are participating in. IP Terminology ? Bit / Byte ? Octet ? Network Address / Sub Address / Host Address ? Broadcast Address ? Sending information to all nodes on a work ? local / limited broadcast– – all works, all nodes ? Directed broadcast – all the bits of host address turned on – all subs and hosts on work ? Broadcast domain – a group of devices receiving broadcast frames initiating from any device within the group. Because they do not forward broadcast frames, broadcast domains are generally surrounded by routers. The Hierarchical IP Addressing Scheme Network ID Host ID 32 Bits w. x. y. z. Example: Class B The IP address is a structure or hierarchical address which consists of a 32bit binary number of 4 octets and is usually displayed in the decimal format (dotted decimal notation). Network Addressing *The class of the Network is determined by the high order bits *Class D is for Multicast and Class E is reserved for Research. Class C Class A Network Address Host Address 0 Class B Network Address Host Address 1 0 Network Address Host Address 1 1 0 0000 0000 0000 0001 1 .. 0111 1110 126 0111 1111 127 1000 0000 128 1011 1111 191 1100 0000 192 1101 1111 223 Address Class Summary Number of Networks 126 16,384 2,097,152 Number of Hosts per Network 16,777,214 65,534 254 Class A Class B Class C Range of Network IDs (First Octet) 1 – 126 128 – 191 192 – 223 Network Addresses: Special Purpose and Guidelines ? Network Address Cannot Be 127 ? 127 is reserved for loopback functions and selfdiagnostic ? is reserved as a loopback address ? Network ID and/or Host ID Cannot Be All Bits Set to 1 ? All 1s means “All works”, or “all nodes” ? 255 is a broadcast addr
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