Quick Answer
The answer is `sudo ss -tlnp`, which is the correct command to list listening TCP ports with process names because it combines four essential flags: `-t` filters for TCP sockets, `-l` restricts output to listening sockets only, `-n` displays numeric port numbers without name resolution, and `-p` attaches the process name to each socket. On the Red Hat Certified System Administrator EX200 exam, this question tests your ability to audit network services efficiently, often appearing in security audit scenarios where you must identify which processes are bound to specific ports without relying on slow DNS lookups. A common trap is using `netstat` instead of `ss`, but `ss` is the modern, faster replacement and the preferred tool in RHEL 8 and 9. Remember the mnemonic "TCP Listens Need Processes" to recall `-t`, `-l`, `-n`, and `-p` in order.
This EX200 practice question tests your understanding of essential tools. 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.
During a security audit, an administrator needs to list all TCP ports on which the system is listening, showing only the port numbers and the associated process names. Which command best achieves this?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Clue: "which command"
Why it matters: Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
netstat -tulpn
Why wrong: Older tool; not installed by default in modern RHEL.
nmap -sT localhost
Why wrong: External scanner; not for local diagnostic.
sudo ss -tlnp
Modern tool; shows listening TCP ports with process info.
lsof -i TCP:1-65535
Why wrong: Shows open files, not just listening ports; requires filtering.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
sudo ss -tlnp
Option C is correct because `sudo ss -tlnp` lists TCP listening sockets with numeric port numbers and process names. The `-t` flag filters for TCP, `-l` shows only listening sockets, `-n` displays numeric addresses/ports (avoiding DNS resolution), and `-p` reveals the process name. This command requires root privileges to see process information, hence `sudo`.
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.
netstat -tulpn
Why it's wrong here
Older tool; not installed by default in modern RHEL.
nmap -sT localhost
Why it's wrong here
External scanner; not for local diagnostic.
sudo ss -tlnp
Why this is correct
Modern tool; shows listening TCP ports with process info.
Clue confirmation
The clue words "best", "which command" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
lsof -i TCP:1-65535
Why it's wrong here
Shows open files, not just listening ports; requires filtering.
Common exam traps
The trap here is that candidates often default to `netstat -tulpn` (Option A) because it is familiar, but Red Hat EX200 emphasizes `ss` as the modern replacement, and the question specifically asks for only TCP ports and process names, making `-u` (UDP) and the lack of `-l` (listening only) in the default `netstat` command incorrect.
Trap categories for this question
Command / output trap
Shows open files, not just listening ports; requires filtering.
Detailed technical explanation
The `ss` command reads socket information directly from the kernel's netlink interface, making it faster and more detailed than the older `netstat` which parses `/proc/net/tcp`. The `-n` flag is critical to avoid DNS lookups that can slow output and hide raw port numbers. In real-world audits, using `sudo` ensures the `-p` flag can access process information, which is otherwise restricted to the user's own processes due to kernel security.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
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
Essential Tools — This question tests Essential Tools — Read the scenario before looking for a memorised answer..
The correct answer is: sudo ss -tlnp — Option C is correct because `sudo ss -tlnp` lists TCP listening sockets with numeric port numbers and process names. The `-t` flag filters for TCP, `-l` shows only listening sockets, `-n` displays numeric addresses/ports (avoiding DNS resolution), and `-p` reveals the process name. This command requires root privileges to see process information, hence `sudo`.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "best", "which command". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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