Communication across a LAN is layer-2 based. IP addresses are layer-3
based. When a host has a given ip address, but not the associatied MAC
address, communication across a LAN is not possible since the layer-3
component is present, but not the layer-2 component. Thus the sending host
has no "identifier" for the receiving host across the layer-2 media. This
situation can only be resolved via a layer-2 broadcast, hence the broadcast
nature of ARP.
ARPs go out with a destination ip address, but a broadcast layer-2 address.
Then the host with the corresponding ip address (if it exists and is
responding) will answer the broadcast ARP with it's own MAC address, thus
giving the sending host a valid layer-3 to layer-2 address mapping.
Hope this helps.
Jamie Byrne
At 04:35 PM 7/3/00 -0400, m. jean stockton wrote:
>Great Question!!! Seems that the only thing that is required is a
>point-2-point communication as the IP address is known.
>
>My 2 cents worth.
>
>
>makeeda
>
>-----Original Message-----
>From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
>Cisco man
>Sent: Monday, July 03, 2000 1:22 AM
>To: [EMAIL PROTECTED]
>Subject: ARP Broadcast
>
>
>Hi All,
>
>Could any one explain why ARP needs to broadcast when looking for the MAC
>address. Why not send a unicast using the given IP address.
>
>Regards to all
>
>Vapian
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