What does a host send as an ARP request when there are no mapping entries in its ARP cache?

What does a host send as an ARP request when there are no mapping entries in its ARP cache?

• A. The MAC address of the destination host.
• B. The local IP address.
• C. The broadcast MAC address.
• D. The subnet mask.

Answer: (C)

When a host needs to communicate with another device on the same network and does not have the required mapping between the IP address and the MAC address in its ARP cache, it sends an ARP (Address Resolution Protocol) request. This request is designed to find out the MAC address corresponding to a specific IP address. The ARP request is sent to the broadcast MAC address, allowing all devices on the local network segment to receive and process the request. The broadcast MAC address, typically represented as FF:FF:FF:FF:FF:FF, ensures that the request is sent to every device in the local broadcast domain since the host does not know the specific MAC address of its destination. Once the intended recipient receives the ARP request, it checks if the IP address specified in the request matches its own. If it does, the device replies with an ARP reply that includes its MAC address. This entire process is crucial for enabling communication within a local area network when only the IP address is known and the MAC address is required to complete the data link layer transmission.

When a host needs to communicate with another device on the same network and does not have the required mapping between the IP address and the MAC address in its ARP cache, it sends an ARP (Address Resolution Protocol) request. This request is designed to find out the MAC address corresponding to a specific IP address.

The ARP request is sent to the broadcast MAC address, allowing all devices on the local network segment to receive and process the request. The broadcast MAC address, typically represented as FF:FF:FF:FF:FF:FF, ensures that the request is sent to every device in the local broadcast domain since the host does not know the specific MAC address of its destination.

Once the intended recipient receives the ARP request, it checks if the IP address specified in the request matches its own. If it does, the device replies with an ARP reply that includes its MAC address. This entire process is crucial for enabling communication within a local area network when only the IP address is known and the MAC address is required to complete the data link layer transmission.