[法学]第06章 ARP和RARP_new.ppt

yn@ yn@ 网络工程系 电子科大通信学院 Chapter 6 ARP and RARP ARP ARP package RARP Addresses Host identifier IP address Physical address Issues A送往E的分组需封装在Ethernet帧中传送 IP地址：全局性 物理地址：本地性 Address Mapping（地址映射） Logical address ?? Physical address ARP and RARP 6.1 ARP Address Resolution Protocol，RFC 826 地址解析协议：IP address ? MAC address 6.1.1 ARP Operation 用户输入命令“ftp 主机名”时的操作 IP Packet and ARP Packet 6.1.2 ARP Packet Encapsulation of ARP packet The byte order of ARP packet Example：Ethernet frame Example: ARP Request Packet Example: ARP Reply Packet 6.1.3 ARP Process Case 1：A ? B In same IP network Lab 2 Case 2：A ? D In different IP network Case 1：A ? B Case 2：A ? D Example A host with IP address 0 and physical address 0xB23455102210 has a packet to send to another host with IP address 5 and physical address 0xA46EF45983AB. The two hosts are on the same Ethernet network. Show the ARP request and reply packets encapsulated in Ethernet frames. Example: ARP Request 6.1.4 Proxy ARP Answer RFC 925: Multi-LAN Address Resolution Explicit subnets Transparent subnets（Extended ARP） RFC 1027: Using ARP to Implement Transparent Subnet Gateways Routers: Explicit subnets Hosts: Transparent subnets Discussion .3向.35发送IP分组 .3广播请求.35的ARP分组，R不转发广播 .35向.3发送IP分组 .35广播请求.62的ARP分组 6.1.5 Gratuitous ARP Duplicate address test 6.2 ARP Package ARP Cache Host（Windows XP） Router（Cisco） 思考 更新ARP绑定时，发现已有的绑定与新的绑定不一样，是保持已有的还是替换它？ 封装IP报文的以太帧中的源MAC和IP报文中的源IP可否用于刷新ARP表项？目的MAC和目的IP呢？ 教材第150页中ARP输入模块描述有误 参见RFC 826中的Packet Reception一节 RFC References RFC 1122: Requirements for Internet Hosts -- Communication Layers Section 2.3.2: ARP cache, ARP packet queue RFC 1812: Requirements for IPv4 Routers Section 3.3.2 RFC 1433: Directed ARP ARP helper address RFC 1868: ARP Extension – UNARP Announce leaving 6.3 RARP Reverse Address Resolution Protocol RFC 903：MAC地址 ? IP地址 RARP Operation Purpose 无盘机器的引导、动态IP地址配置 Packet format 与ARP分组相同 Operation：3 – RARP request，4 – RARP reply Ethernet frame encapsulation 类型：0x8035 Oper