Which option sends IP packets with a specific protocol number in the IP header for discovery?

Which option sends IP packets with a specific protocol number in the IP header for discovery?

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

Answer: (A)

Disco­­very probes often ride on ICMP, which is identified in the IP header by the protocol number 1. When you send a packet with this protocol field set to ICMP, the network stack treats the payload as an ICMP message and can generate a reply to indicate whether the host is reachable. This is the essence of the ping approach: a simple ICMP Echo Request used to discover alive hosts. The other options refer to more specific ICMP message types or to a different transport protocol. ICMP timestamp or ICMP address mask messages are particular ICMP kinds, not the general mechanism used for quick reachability checks. TCP SYN ping uses the TCP protocol (protocol number 6), which is a different transport layer and not the ICMP-based discovery method.

Disco­­very probes often ride on ICMP, which is identified in the IP header by the protocol number 1. When you send a packet with this protocol field set to ICMP, the network stack treats the payload as an ICMP message and can generate a reply to indicate whether the host is reachable. This is the essence of the ping approach: a simple ICMP Echo Request used to discover alive hosts.

The other options refer to more specific ICMP message types or to a different transport protocol. ICMP timestamp or ICMP address mask messages are particular ICMP kinds, not the general mechanism used for quick reachability checks. TCP SYN ping uses the TCP protocol (protocol number 6), which is a different transport layer and not the ICMP-based discovery method.