This LFCS practice question tests your understanding of networking. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which TWO commands can display a list of active TCP connections listening on the system? (Choose two.)
ss -tuln
Modern replacement for netstat; shows listening sockets.
nmcli connection show
Why wrong: Shows NetworkManager connection profiles, not listening ports.
ifconfig
Why wrong: Shows interface configuration, not listening ports.
netstat -tuln
Displays listening TCP and UDP ports.
ip route show
Why wrong: Shows routing table, not listening ports.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
ss -tuln
Option A is correct because `ss -tuln` displays TCP (`-t`) and UDP (`-u`) sockets in a listening (`-l`) state with numeric (`-n`) addresses and ports, directly showing active TCP listening connections. Option D is correct because `netstat -tuln` performs the same function, listing TCP and UDP listening sockets with numeric output, and is the traditional tool for this purpose.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
ss -tuln
Why this is correct
Modern replacement for netstat; shows listening sockets.
Related concept
Read the scenario before looking for a memorised answer.
nmcli connection show
Why it's wrong here
Shows NetworkManager connection profiles, not listening ports.
ifconfig
Why it's wrong here
Shows interface configuration, not listening ports.
netstat -tuln
ip route show
Why it's wrong here
Shows routing table, not listening ports.
Common exam traps
The trap here is that candidates confuse commands that show network configuration (like `ifconfig` or `ip route`) with commands that show active socket states, leading them to pick options that display interface or routing information instead of listening TCP ports.
Trap categories for this question
Command / output trap
Shows NetworkManager connection profiles, not listening ports.
Detailed technical explanation
Both `ss` and `netstat` read socket information from the `/proc/net/tcp` and `/proc/net/tcp6` files (or use netlink sockets in the case of `ss`), which contain the kernel's TCP control block data. The `-l` flag filters for sockets in the LISTEN state (TCP state machine, RFC 793), which is distinct from ESTABLISHED or TIME_WAIT states. In modern Linux distributions, `ss` is preferred over `netstat` because it uses netlink for faster and more detailed output, especially under high connection counts.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the LFCS exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Networking — This question tests Networking — Read the scenario before looking for a memorised answer..
The correct answer is: ss -tuln — Option A is correct because `ss -tuln` displays TCP (`-t`) and UDP (`-u`) sockets in a listening (`-l`) state with numeric (`-n`) addresses and ports, directly showing active TCP listening connections. Option D is correct because `netstat -tuln` performs the same function, listing TCP and UDP listening sockets with numeric output, and is the traditional tool for this purpose.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
This LFCS practice question is part of Courseiva's free Linux Foundation certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the LFCS exam.
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