On an Ethernet network, ARP packets are classified into ARP Request packets and ARP Response packets. In the initial communication phase, how are ARP Request packets transmitted on the network?
The Address Resolution Protocol (ARP) is used to map IP addresses to MAC addresses in a local network. ARP operates at the data link layer (Layer 2) of the OSI model and is essential for communication within a LAN.
ARP Request :
When a device needs to communicate with another device on the same network but does not know the destination's MAC address, it sends an ARP Request .
Since the sender does not know the MAC address of the destination, it cannot send the request directly to the destination using unicast. Instead, the ARP Request is sent as a broadcast packet to all devices on the local network.
The broadcast packet has a destination MAC address of FF:FF:FF:FF:FF:FF, which ensures that all devices on the network receive the packet.
ARP Response :
The device with the matching IP address responds with an ARP Reply , which is sent as a unicast packet back to the requesting device.
Why Not Other Options?
Anycast : This involves sending packets to the nearest device in a group of devices sharing the same IP address. ARP does not use anycast.
Unicast : ARP Requests cannot be sent as unicast because the sender does not yet know the destination's MAC address.
Multicast : Multicast is used for sending packets to a specific group of devices, but ARP Requests are sent to all devices on the network, making broadcast the correct choice.
Thus, ARP Requests are transmitted as broadcast packets .
References:
HCIA Huawei ACCESS Official Documentation , Chapter: ARP Protocol and Operation.
Ethernet Networking Fundamentals by Huawei.
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