This XK0-005 practice question tests your understanding of troubleshooting. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Exhibit
# /etc/nftables.conf
flush ruleset
table inet filter {
chain input {
type filter hook input priority 0; policy drop;
tcp dport 22 accept
tcp dport 80 accept
tcp dport 443 accept
ip protocol icmp accept
ct state established,related accept
}
}
ping 10.0.0.1
PING 10.0.0.1 (10.0.0.1) 56(84) bytes of data.
From 10.0.0.2 icmp_seq=1 Destination Port Unreachable
Refer to the exhibit. An administrator can SSH to the server but cannot ping 10.0.0.1. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
# /etc/nftables.conf
flush ruleset
table inet filter {
chain input {
type filter hook input priority 0; policy drop;
tcp dport 22 accept
tcp dport 80 accept
tcp dport 443 accept
ip protocol icmp accept
ct state established,related accept
}
}
ping 10.0.0.1
PING 10.0.0.1 (10.0.0.1) 56(84) bytes of data.
From 10.0.0.2 icmp_seq=1 Destination Port Unreachable
A
The destination host 10.0.0.1 is not responding to ping due to a firewall or ICMP being disabled on that host.
The 'Destination Port Unreachable' message indicates the remote host received the ping but sent back an ICMP unreachable, likely because ping is disabled or filtered on that host.
B
The ping is being blocked by the nftables output chain, which is not configured.
Why wrong: The output chain is not shown; but the error is from the remote host.
C
ICMP is blocked by the nftables input chain policy drop.
Why wrong: The rule 'ip protocol icmp accept' should allow ICMP.
D
The destination host 10.0.0.1 does not have a route back.
Why wrong: The error 'Destination Port Unreachable' typically indicates no process listening, not routing.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The destination host 10.0.0.1 is not responding to ping due to a firewall or ICMP being disabled on that host.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
The destination host 10.0.0.1 is not responding to ping due to a firewall or ICMP being disabled on that host.
Why this is correct
The 'Destination Port Unreachable' message indicates the remote host received the ping but sent back an ICMP unreachable, likely because ping is disabled or filtered on that host.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
The ping is being blocked by the nftables output chain, which is not configured.
Why it's wrong here
The output chain is not shown; but the error is from the remote host.
✗
ICMP is blocked by the nftables input chain policy drop.
Why it's wrong here
The rule 'ip protocol icmp accept' should allow ICMP.
✗
The destination host 10.0.0.1 does not have a route back.
Why it's wrong here
The error 'Destination Port Unreachable' typically indicates no process listening, not routing.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Trap categories for this question
Command / output trap
The output chain is not shown; but the error is from the remote host.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this XK0-005 question in full detail.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related XK0-005 NAT questions on configuration and troubleshooting.
Troubleshooting — This question tests Troubleshooting — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The destination host 10.0.0.1 is not responding to ping due to a firewall or ICMP being disabled on that host.
What should I do if I get this XK0-005 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related XK0-005 NAT questions on configuration and troubleshooting.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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