問70
頻出度★★★
サブネットマスクの役割として, 適切なものはどれか。
平成28年度 春期 ITパスポート試験 問70
テクノロジ系ネットワーク › ネットワーク応用
This question's explanation and your answers so far.
解説
問 70
Incorrectア
Determining the MAC address on an Ethernet from an IP address is the role of ARP (Address Resolution Protocol), not of a subnet mask.
- イ
正解 A subnet mask is applied bit by bit to an IP address (an AND operation): the bits set to 1 mark the network address part and the bits set to 0 mark the host address part. This splits a single IP address into which network it belongs to (the network address) and which device it is within that network (the host address). Choice イ correctly describes exactly this role — distinguishing the network address from the host address of each individual computer — so it is the correct answer.
Incorrectウ
Mapping global IP addresses to private IP addresses is the role of NAT (NAPT / IP masquerade), not of a subnet mask.
Incorrectエ
Mapping a domain name to an IP address is the role of DNS (Domain Name System), not of a subnet mask.
ここがポイント
- A subnet mask splits an IP address into a network address part and a host address part (the network address is obtained by ANDing the mask with the IP address).
- Distinguish the roles of easily confused neighboring concepts: MAC resolution = ARP, global/private address translation = NAT, domain name resolution = DNS.
用語