问题一 请问一下 ARP 是让主机可由已知的 protocol address (IP address)询问 来得到 hardware address (MAC address) 如果在一台 end host 与 switch 间架一个 bridge 把 ARP 全都 filter 掉 那 end host 有其它办法可以得到 hardware address 吗? 问题二 看了一下 RFC826 http://www.faqs.org/rfcs/rfc826.html 在处理 ARP 的封包时的 algorithm 如下 ?Do I have the hardware type in ar$hrd? Yes: (almost definitely) [optionally check the hardware length ar$hln] ?Do I speak the protocol in ar$pro? Yes: [optionally check the protocol length ar$pln] Merge_flag := false If the pair <protocol type, sender protocol address> is already in my translation table, update the sender hardware address field of the entry with the new information in the packet and set Merge_flag to true. ?Am I the target protocol address? Yes: If Merge_flag is false, add the triplet <protocol type, sender protocol address, sender hardware address> to the translation table. ?Is the opcode ares_op$REQUEST? (NOW look at the opcode!!) Yes: Swap hardware and protocol fields, putting the local hardware and protocol addresses in the sender fields. Set the ar$op field to ares_op$REPLY Send the packet to the (new) target hardware address on the same hardware on which the request was received. 按上面标颜色的部份 应该会先 add sender information 至 ARP table内 才会去判断该封包的 opcode 试了一下发现 在 ARP table 没有该 sender 的记录情况下 收到 ARP reply 却不会新增 sender 的记录 是因为 ARP reply 在更前面就处理结束了吗? 还是 RFC826 有被其它 RFC 所更新? (因为我并没有找到) --

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