Which protocol is responsible for resolving IP addresses to MAC addresses in IPv4 networks?
The correct answer and explanation is:
The protocol responsible for resolving IP addresses to MAC addresses in IPv4 networks is the Address Resolution Protocol (ARP).
ARP is a network layer protocol used to map an IP address to its corresponding physical MAC (Media Access Control) address within a local area network (LAN). It operates within a typical IPv4 network where devices communicate using both logical IP addresses and physical MAC addresses.
Here’s how ARP works:
- ARP Request: When a device (e.g., a computer) needs to communicate with another device on the same network, it first checks its ARP cache to see if it has the MAC address corresponding to the IP address of the destination. If the entry is not found, the device broadcasts an ARP request to the entire local network.
- ARP Reply: The device with the matching IP address replies with an ARP response, which includes its MAC address. This reply is sent directly to the requesting device.
- Caching: The requesting device receives the ARP reply and caches the IP-to-MAC mapping in its ARP table for future use. This reduces the need for frequent ARP requests.
- Expiration: ARP entries are not permanent. They have a time-to-live (TTL) period after which they expire and are removed from the cache to ensure that outdated mappings do not persist.
ARP is critical for efficient communication within IPv4 networks because IP addresses are used to route packets at the network layer, while MAC addresses are used to deliver data frames at the data link layer. The mapping between IP and MAC addresses allows devices to correctly address and route frames within the local network.
Despite its effectiveness, ARP is vulnerable to certain attacks, such as ARP spoofing, where a malicious actor can send fake ARP messages to associate their MAC address with another device’s IP address, enabling them to intercept or alter network traffic. Therefore, network administrators often implement security measures like static ARP entries or use of dynamic ARP inspection (DAI) to mitigate these risks.