令和5年度 ITパスポート試験問97

This question's explanation and your answers so far.

問97

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。

出典　令和5年度 ITパスポート試験問97

解説

問 97

Incorrectア
Deriving the MAC address on the same LAN from an IP address is the role of ARP (Address Resolution Protocol), not the role of a subnet mask.
イ
正解 The correct answer is イ. A subnet mask is a value that indicates the boundary dividing an IP address into a network-address portion and a host-address portion, and it defines how many bits, counting from the start of the IP address, are used for the network address. For example, 255.255.255.0 means the first 24 bits are the network portion, and a device uses this mask to determine whether a communication partner is inside or outside the same network. Therefore イ is correct.
Incorrectウ
Automatically obtaining TCP/IP configuration information (such as IP address, subnet mask, and default gateway) just by connecting to a LAN is a function of DHCP, not the role of the subnet mask itself.
Incorrectエ
Associating a communication partner's domain name with an IP address (performing name resolution) is the role of DNS, not the role of a subnet mask.

ここがポイント

A subnet mask defines the boundary between the network portion and the host portion of an IP address and indicates how many bits, counting from the start, form the network address.
Being able to distinguish the differences in roles among ARP, DHCP, and DNS is the key point of this question.

用語

解答問97イ