ipmacaddresstranslation-文庫(kù)吧資料
2024-10-20 15:41本頁(yè)面
【正文】 the pair (IB ,PB ) CS 640 5 ARP Implementation ? ARP Packet Details – HardwareType: type of physical work (., Ether) – ProtocolType: type of higher layer protocol (., IP) – HLEN amp。 PLEN: length of physical and protocol addresses ? Provides for flexibility to handle a variety of work technologies – Operation: request or response – Source/TargetPhysical/Protocol addresses ? Notes – Table entries timeout in about 10 minutes (caching is important) – Update table with source when you are the target – Update table even if there is already an entry – Do not refresh table entries upon reference – IP addresses are assigned independently of a systems HW addresses CS 640 6 ARP Packet Format T argetHardwareAddr (bytes 2 – 5) T argetProtocolAddr (bytes 0 – 3) SourceProtocolAddr (bytes 2 – 3) Hardware type = 1 ProtocolT ype = 0x0800 SourceHardwareAddr (bytes 4 – 5) T argetHardwareAddr (bytes 0 – 1) SourceProtocolAddr (bytes 0 – 1) HLen = 48 PLen = 32 Operation SourceHardwareAddr (bytes 0 – 3) 0 8 16 31 CS 640 7 Determining an IP Address at Startup ? How does a machine without permanent storage determine its IP address? – OS images with specific IP’s cannot be used on multiple machines – Critical for work appliances or embedded systems ? Use the work to obtain an IP from a remote server – System must use its physical address to to municate – Requests address from server which maintains table of IP’s – System doesn’t know the se
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