Which ICMP method queries for the address mask to obtain subnet mask information?

• A. ICMP timestamp ping
• B. ICMP address mask ping
• C. TCP SYN ping
• D. IP protocol ping

Answer: (B)

The main concept here is identifying the ICMP message type that is specifically used to discover the subnet mask of a device. The ICMP address mask ping sends an Address Mask Request to a host, and if the device supports it, it replies with an Address Mask Reply that includes the subnet mask. This is the exact mechanism used to obtain subnet mask information from a target.

Other options don’t serve this purpose. An ICMP timestamp ping asks the remote for the current time to measure clock skew, not network addressing details. A TCP SYN ping is a TCP-level probe used to check liveness via a SYN/ACK exchange, not an ICMP address mask query. An IP protocol ping isn’t a standard method for learning subnet masks.