The answer is that there is no route to the private subnet via eth1, which is the most likely cause when a Linux client with two interfaces cannot access the private LAN. Without a specific route for the private subnet in the routing table, packets destined for that LAN are sent out via the default route through eth0 to the internet, where they fail to reach their target. This tests your understanding of the Linux routing table and how the kernel selects paths for outbound traffic, a core objective in the Linux Professional Institute Certification Level 2 LPIC-2 exam under network configuration. A common trap is assuming that simply having an interface connected to the LAN is enough, but the kernel requires an explicit route to direct traffic through that interface. Use `ip route` to verify; if the private subnet is missing, add it with `ip route add 192.168.1.0/24 dev eth1`. Memory tip: “No route, no root to the LAN”—without a route, packets have no path.
LPIC-2 Network Client Management Practice Question
This LPIC-2 practice question tests your understanding of network client management. 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.
A Linux client is configured with two network interfaces: eth0 (connected to the internet) and eth1 (connected to a private LAN). The default route is set to eth0. The client can access the internet but cannot access hosts on the private LAN. 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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
There is no route to the private subnet via eth1.
Option D is correct because without a route to the private subnet via eth1, the client has no way to forward packets destined for the private LAN out of eth1. The default route via eth0 only handles traffic for destinations not explicitly matched by other routes; if the private subnet is not in the routing table, packets to that subnet will be sent to the default gateway (internet) and fail. The `ip route` command would show the missing entry, and adding a static route (e.g., `ip route add 192.168.1.0/24 dev eth1`) resolves the issue.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
A firewall on the client is blocking ICMP packets on eth1.
Why it's wrong here
Firewall could block ping, but the problem is likely routing since internet works.
✗
The eth1 interface is not configured with an IP address.
Why it's wrong here
The question does not indicate misconfiguration; if eth1 is up and has an IP, it should work with a route.
Without a specific route, traffic to the private subnet may be sent to the default gateway (eth0) and fail.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume a missing IP address or DHCP lease is the cause, but the question explicitly states the client has two configured interfaces—the real issue is the absence of a route to the private subnet, which is a classic LPIC-2 routing table pitfall.
Detailed technical explanation
How to think about this question
Under the hood, the Linux kernel uses the routing table (FIB) to determine the next hop for each packet. When a packet's destination IP matches a subnet in the routing table, it is forwarded via the associated interface; if no match exists, the default route is used. A common real-world scenario is when a client has multiple interfaces and the default route is set to the internet-facing interface, but the private subnet route is missing—this often happens after a network restart or when using NetworkManager without proper static route configuration.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network Client Management — This question tests Network Client Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: There is no route to the private subnet via eth1. — Option D is correct because without a route to the private subnet via eth1, the client has no way to forward packets destined for the private LAN out of eth1. The default route via eth0 only handles traffic for destinations not explicitly matched by other routes; if the private subnet is not in the routing table, packets to that subnet will be sent to the default gateway (internet) and fail. The `ip route` command would show the missing entry, and adding a static route (e.g., `ip route add 192.168.1.0/24 dev eth1`) resolves the issue.
What should I do if I get this LPIC-2 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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?
Read the scenario before looking for a memorised answer.
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