A host is trying to send a packet to a device on a remote LAN segment, but there are currently no mappings in its ARP cache. How will the device obtain a destination MAC address?
ARP (Address Resolution Protocol) cache
When a host needs to send a packet to a device on a remote LAN segment and there are no mappings in its ARP (Address Resolution Protocol) cache, it will follow a process called ARP resolution to obtain the destination MAC address.
Here is the step-by-step process:
1. The host checks its ARP cache to see if it has already discovered the MAC address for the destination IP address. If there is no entry in the ARP cache, it proceeds to the next step.
2. The host broadcasts an ARP Request message to the local network. In this request, the host includes the IP address of the target device it wants to communicate with.
3. All devices on the local network receive the ARP Request message. However, only the device with the matching IP address specified in the ARP Request will respond.
4. The device with the matching IP address generates an ARP Reply message. This reply contains its MAC address as well as the IP address mentioned in the original ARP Request.
5. The host receives the ARP Reply message, updates its ARP cache with the mapping of the target device’s IP address to its MAC address, and proceeds with sending the packet to the destination device using the MAC address obtained from the ARP Reply.
It is worth noting that once the host has obtained the destination MAC address through ARP resolution, it caches this mapping to optimize future communication with the same device. This caching helps avoid the overhead of repeating the ARP resolution process for subsequent communication with the same device.
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