Question

What two pieces of information does nmap need to estimate network path distance?

A. IP address and TTL
B. TTL and operating system
C. Operating system and BGP flags
D. TCP flags and IP address

Answer 1

Nmap estimates the network path distance using the IP address and TTL value. TTL determines the number of hops a packet can take, while the IP address identifies the target.

Step-by-step explanation:

Nmap, a network scanning tool, requires two specific pieces of information to estimate the network path distance. The pieces of information needed are the IP address and the Time to Live (TTL) value. The TTL is a field in the IP header that specifies the maximum number of hops a packet is allowed before it should be discarded. Network path distance refers to the number of hops (routers or switches) that a packet traverses to reach its destination. Nmap uses the initial TTL value set by the sender and the remaining TTL value upon arrival to estimate the number of hops. The IP address is necessary to identify the target of the scanning process. Operating systems and BGP flags are not directly related to estimating the number of hops, while TCP flags are generally used for different types of network analysis, such as assessing the state of a TCP connection.

Answer 2

IP address and TTL.

Thus the correct option is (A).

Step-by-step explanation:

Nmap utilizes the combination of IP address and Time-to-Live (TTL) values to estimate network path distance. The Time-to-Live value in an IP packet represents the maximum number of hops or routers the packet can traverse before being discarded. By sending packets with varying TTL values and observing the response, Nmap can deduce the number of hops required to reach the target, providing an estimate of the network path distance. The IP address is essential for specifying the target destination.

This technique leverages the fact that each router along the network path decrements the TTL value, and when the TTL reaches zero, the router discards the packet and sends an ICMP Time Exceeded message back to the source. By manipulating the TTL and analyzing the responses, Nmap can infer the network path's length. This method is valuable for network reconnaissance, helping to understand the topology and characteristics of a target network.

In summary, Nmap's estimation of network path distance relies on the IP address to designate the target and the TTL to gauge the number of hops. This approach is a fundamental part of Nmap's arsenal for network exploration and mapping.

Thus the correct option is (A).