ITPEC IP October 2022 Question 30

Separating the network address from the host address in an IP address — the subnet mask marks which bits of the address belong to the network.

A subnet mask is 32 bits written like an IP address: its 1 bits cover the network part and its 0 bits the host part. ANDing an address with the mask gives the network address. For 192.168.10.25 with mask 255.255.255.0 (/24), the network address is 192.168.10.0 and the host part is 25. A computer compares network addresses this way to decide whether a destination is on its own network, to be reached directly, or elsewhere, to be sent via the default gateway.

Answer (b)

Why not others:

• •(a) — finding the MAC address on an Ethernet from an IP address is ARP
• •(c) — mapping private IP addresses to a global IP address between the internal network and the Internet is NAT (NAPT)
• •(d) — mapping a domain name to an IP address is DNS

Key rule: Match each job to its mechanism: the subnet mask splits network and host parts, ARP finds a MAC address, NAT translates private and global addresses, DNS resolves names.

Networks · AI-written, may contain errors