問65
頻出度★★★
DNS サーバの役割に関する記述として，適切なものはどれか。
令和8年度 ITパスポート試験 問65
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 65
Incorrectア
Accessing a web server on the internet on behalf of a PC on the LAN and returning the response to the PC is the role of a 'proxy server', not a DNS server.
Incorrectイ
Accepting requests to send and receive files between a PC and a server and transferring the files is the role of a 'file transfer service' such as an FTP server, not a description of a DNS server that performs name resolution.
Incorrectウ
Automatically assigning IP addresses to a PC and notifying it of the subnet mask and the IP address of the default gateway is the role of a 'DHCP server', a function separate from a DNS server.
- エ
正解 A DNS (Domain Name System) server maps the human-friendly 'domain name' to the 'IP address' required for communication, and converts between the two. For example, when you query the domain name 'www.example.co.jp', it returns the corresponding IP address (forward lookup). Conversely, it can also obtain a domain name from an IP address (reverse lookup). Choice エ accurately states both forward and reverse lookup, and is exactly the definition of a DNS server's role, so it is the correct answer.
ここがポイント
- The role of a DNS server = mutual conversion between a domain name and an IP address (name resolution). Domain name to IP address is forward lookup; IP address to domain name is reverse lookup.
- Distinguish similar 'server roles': do not confuse a proxy server (proxy access and relaying), an FTP server (file transfer), and a DHCP server (automatic assignment of IP addresses, etc.).
用語