The packet is forwarded via eth1 to 10.0.0.1 because the kernel applies the routing table longest prefix match rule, selecting the most specific route that contains the destination address. While a default route of 0.0.0.0/0 covers all addresses, the route 0.0.0.0/1 is more specific, covering only 0.0.0.0 through 127.255.255.255, and since 8.8.8.8 falls within that range, the /1 prefix wins. On the Linux Professional Institute Certification Level 2 LPIC-2 exam, this tests your understanding of how the kernel resolves overlapping routes—a common trap is assuming the default route always applies, but the longest prefix match always overrides a less specific entry. Remember that a /1 prefix is actually half the IPv4 space, so it is not a default; it is a more precise match. A useful memory tip: "Longer is stronger"—the more bits in the network mask, the higher the priority, regardless of the route's numeric value.
LPIC-2 Advanced Networking Configuration Practice Question
This LPIC-2 practice question tests your understanding of advanced networking configuration. 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.
Exhibit
Refer to the exhibit.
```
# ip route show table 100
192.168.10.0/24 dev eth0 scope link
0.0.0.0/1 via 10.0.0.1 dev eth1
```
```
# ip rule show
0: from all lookup local
32765: from 192.168.10.0/24 lookup 100
32766: from all lookup main
32767: from all lookup default
```
Given the exhibited routing table and rules, what will happen to a packet originating from IP 192.168.10.50 destined to 8.8.8.8?
Refer to the exhibit.
```
# ip route show table 100
192.168.10.0/24 dev eth0 scope link
0.0.0.0/1 via 10.0.0.1 dev eth1
```
```
# ip rule show
0: from all lookup local
32765: from 192.168.10.0/24 lookup 100
32766: from all lookup main
32767: from all lookup default
```
A
The packet is dropped because no matching route exists.
Why wrong: There is a default route in table 100, so the packet is not dropped.
B
The packet is forwarded via eth1 because of the 0.0.0.0/1 route.
Why wrong: The route 0.0.0.0/1 covers 8.8.8.8, but it is not a default route; the default route via 10.0.0.1 is used.
C
The packet is forwarded via eth1 to 10.0.0.1.
Table 100 has a default route via 10.0.0.1 for this source.
D
The packet is forwarded via eth0 to the default gateway in the main table.
Why wrong: The rule for this source uses table 100, not the main table.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The packet is forwarded via eth1 to 10.0.0.1.
The routing table shows a default route of 0.0.0.0/0 via eth0, but also includes a more specific route 0.0.0.0/1 via eth1 with next-hop 10.0.0.1. Since the destination 8.8.8.8 falls within the 0.0.0.0/1 prefix (which covers 0.0.0.0 to 127.255.255.255), the kernel performs a longest prefix match and selects the /1 route over the /0 default, forwarding the packet via eth1 to 10.0.0.1.
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.
✗
The packet is dropped because no matching route exists.
Why it's wrong here
There is a default route in table 100, so the packet is not dropped.
✗
The packet is forwarded via eth1 because of the 0.0.0.0/1 route.
Why it's wrong here
The route 0.0.0.0/1 covers 8.8.8.8, but it is not a default route; the default route via 10.0.0.1 is used.
✓
The packet is forwarded via eth1 to 10.0.0.1.
Why this is correct
Table 100 has a default route via 10.0.0.1 for this source.
Related concept
Read the scenario before looking for a memorised answer.
✗
The packet is forwarded via eth0 to the default gateway in the main table.
Why it's wrong here
The rule for this source uses table 100, not the main table.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume 0.0.0.0/0 is the only default route and ignore the more specific 0.0.0.0/1 route, leading them to incorrectly select the default gateway in the main table instead of recognizing the longer prefix match.
Detailed technical explanation
How to think about this question
The 0.0.0.0/1 route is a less common but valid CIDR prefix that covers the first half of the IPv4 address space (0.0.0.0–127.255.255.255). This is sometimes used in policy routing or load balancing setups to split traffic between two default gateways. The kernel's routing decision always uses the longest prefix match algorithm, so a /1 route beats a /0 route regardless of metric or administrative distance.
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.
Advanced Networking Configuration — This question tests Advanced Networking Configuration — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The packet is forwarded via eth1 to 10.0.0.1. — The routing table shows a default route of 0.0.0.0/0 via eth0, but also includes a more specific route 0.0.0.0/1 via eth1 with next-hop 10.0.0.1. Since the destination 8.8.8.8 falls within the 0.0.0.0/1 prefix (which covers 0.0.0.0 to 127.255.255.255), the kernel performs a longest prefix match and selects the /1 route over the /0 default, forwarding the packet via eth1 to 10.0.0.1.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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