問97
頻出度★★★
サブネットマスクの用法に関する説明として, 適切なものはどれか。
平成30年度 秋期 ITパスポート試験 問97
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 97
- ア
正解 A subnet mask is used to indicate the boundary of “where the network address part ends and where the host address part begins” within an IP address. When the IP address and the subnet mask are lined up in binary, the bits that are 1 in the mask represent the network address part, and the bits that are 0 represent the host address part. For example, with 255.255.255.0 (whose leading 24 bits are 1 in binary), the upper 24 bits are the network part and the lower 8 bits are the host part. Therefore, choice “ア”, which says it is used to indicate this boundary, is correct.
Incorrectイ
Mutually translating between private IP addresses and global IP addresses is the role of NAT (including NAPT), not the purpose of a subnet mask.
Incorrectウ
Obtaining the MAC address on the same Ethernet from a communication partner’s IP address is the role of ARP, not the purpose of a subnet mask.
Incorrectエ
Automatically assigning network information such as IP addresses to computers within a network is the role of DHCP, not the purpose of a subnet mask.
ここがポイント
- A subnet mask indicates the boundary that divides an IP address into a network address part and a host address part (mask bits of 1 are the network part, bits of 0 are the host part).
- NAT (address translation), ARP (IP→MAC), and DHCP (automatic IP assignment) are mechanisms separate from a subnet mask; do not confuse them.
用語