ARP packets are used to discover all active devices in the IPv4 range even when their presence is hidden by restrictive firewalls. What is this technique called?

ARP packets are used to discover all active devices in the IPv4 range even when their presence is hidden by restrictive firewalls. What is this technique called?

• A. ARP ping scan
• B. IP Scanner
• C. SYN scan
• D. ICMP ping scan

Answer: (A)

ARP ping scan leverages the Address Resolution Protocol to map who is active on a local IPv4 subnet. It sends ARP requests (for each IP in the target range) as broadcasts. If a device owns a given IP, it replies with its MAC address, revealing its presence. Because ARP operates at the local network layer, these responses come directly from hosts on the same broadcast domain, and firewalls that block higher-layer probes like ICMP echo requests or TCP SYN scans often don’t stop ARP replies. This makes ARP-based discovery effective even when restrictive firewalls hide devices from other scanning techniques. Keep in mind that ARP scanning is limited to the local network; routers won’t forward ARP, so hosts behind different subnets aren’t discovered.

ARP ping scan leverages the Address Resolution Protocol to map who is active on a local IPv4 subnet. It sends ARP requests (for each IP in the target range) as broadcasts. If a device owns a given IP, it replies with its MAC address, revealing its presence. Because ARP operates at the local network layer, these responses come directly from hosts on the same broadcast domain, and firewalls that block higher-layer probes like ICMP echo requests or TCP SYN scans often don’t stop ARP replies. This makes ARP-based discovery effective even when restrictive firewalls hide devices from other scanning techniques. Keep in mind that ARP scanning is limited to the local network; routers won’t forward ARP, so hosts behind different subnets aren’t discovered.