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LFCS · Question #481

Which of the following lines would you expect to see in the file /etc/protocols?

The correct answer is D. udp 17 UDP. The /etc/protocols file lists network protocol names and their corresponding protocol numbers, adhering to a specific format.

Submitted by jian89· Apr 18, 2026Networking

Question

Which of the following lines would you expect to see in the file /etc/protocols?

Options

  • Ain.tftpd: LOCAL
  • Btftp dgram udp wait root /usr/sbin/tcpd in.tftpd
  • Ctftp 69/udp
  • Dudp 17 UDP

How the community answered

(24 responses)
  • B
    4% (1)
  • C
    8% (2)
  • D
    88% (21)

Why each option

The `/etc/protocols` file lists network protocol names and their corresponding protocol numbers, adhering to a specific format.

Ain.tftpd: LOCAL

This format is incorrect for `/etc/protocols`; it resembles an entry that might be found in a configuration file like `/etc/services` or a service configuration.

Btftp dgram udp wait root /usr/sbin/tcpd in.tftpd

This line describes an `inetd` or `xinetd` service configuration, specifying how a daemon should be invoked, and does not belong in `/etc/protocols`.

Ctftp 69/udp

This line describes a service and its port/protocol, typically found in `/etc/services`, not `/etc/protocols`.

Dudp 17 UDPCorrect

The line "udp 17 UDP" correctly lists the protocol name (udp), its assigned protocol number (17), and an alias (UDP), which is the standard format for entries in the `/etc/protocols` file. This file is used by network services to look up protocol information.

Concept tested: /etc/protocols file format

Topics

#/etc/protocols#network protocols#networking configuration#system files

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