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Table Of Contents  The TCP/IP Guide
 9  TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)
      9  TCP/IP Network Interface / Internet "Layer Connection" Protocols
           9  Address Resolution and the TCP/IP Address Resolution Protocol (ARP)
                9  Address Resolution Concepts and Issues

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Address Resolution Through Direct Mapping
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The Need For Address Resolution
(Page 2 of 3)

Converting Layer Three Addresses to Layer Two: Address Resolution

The basic problem is that IP addresses are too high level for the physical hardware on networks to deal with; they don't understand what they are. When your request shows up at the router that connects to The TCP/IP Guide, it can see the http://www.tcpipguide.com server's IP address, but that isn't helpful: it needs to send to server's MAC address.

The identical issue exists even with communication between devices on a LAN. Even if the Web server is sitting on the same desk as the client, the communication is logically at the IP layer, but must also be accomplished at the data link layer. This means we need a way of translating between the addresses at these two layers. This process is called address resolution.

Key Concept: Address resolution is required because internetworked devices communicate logically using layer three addresses, but the actual transmissions between devices take place using layer two (hardware) addresses.



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Version 3.0 - Version Date: September 20, 2005

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