The answer is to add the physical NIC (eth0) as a port to the Linux bridge. A Linux bridge functions as a virtual Layer 2 switch, and without the physical NIC attached, the bridge is an isolated network segment—the VM’s tap interface can communicate with the host but has no path to the external network. By adding eth0 as a bridge port, you extend the bridge’s broadcast domain to the corporate network, allowing the VM to reach external hosts via the host’s upstream router. On the ENCOR 350-401 exam, this scenario tests your understanding of bridging and KVM networking; a common trap is assuming the host’s IP address on eth0 will automatically route traffic for the bridge, but the bridge must own the physical port to forward frames. Remember the memory tip: “A bridge without a physical port is a floating island—connect the cable to reach the mainland.”
CCNP Virtual Machines and Hypervisors Practice Question
This 350-401 practice question tests your understanding of virtual machines and hypervisors. 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.
An engineer is deploying a Linux virtual machine on a KVM hypervisor. The VM needs to be connected to a virtual network that provides isolation from other VMs on the same host but allows communication with the host and external networks. The engineer creates a Linux bridge and attaches the VM's tap interface to it. However, the VM cannot reach the external network. The host has a physical NIC (eth0) connected to the corporate network. What is the missing configuration step?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add the physical NIC (eth0) as a port to the Linux bridge.
A Linux bridge acts like a virtual switch. To allow the VM to reach the external network, the physical NIC (eth0) must be added as a port to the bridge. This bridges the VM's tap interface with the host's physical network, enabling Layer 2 connectivity to the corporate network and upstream routing.
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.
✓
Add the physical NIC (eth0) as a port to the Linux bridge.
Why this is correct
Correct because the bridge must include the physical NIC to forward traffic to the external network.
Related concept
Read the scenario before looking for a memorised answer.
✗
Configure a default gateway on the VM's network interface.
Why it's wrong here
Incorrect because the VM likely has a gateway, but the bridge is not connected to the physical network.
✗
Assign an IP address to the Linux bridge interface.
Why it's wrong here
Incorrect because the bridge interface IP is for the host, not for VM connectivity.
✗
Enable IP forwarding and configure NAT on the host.
Why it's wrong here
Incorrect because NAT is not needed if the bridge is connected to the physical network.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse bridging with NAT or routing, assuming that IP forwarding or NAT is required for external access, when in fact a bridged setup simply needs the physical NIC as a bridge port to extend Layer 2 connectivity.
Detailed technical explanation
How to think about this question
When a physical NIC is added to a Linux bridge, the bridge becomes a transparent Layer 2 switch between the VM's tap interface and the physical network. The host's IP configuration typically moves from eth0 to the bridge interface (e.g., br0) to maintain connectivity. In production, this is common for VM direct access to the physical LAN, but it requires the bridge to have an IP address (often from DHCP) and the physical NIC to be in promiscuous mode to forward all frames.
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.
Virtual Machines and Hypervisors — This question tests Virtual Machines and Hypervisors — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Add the physical NIC (eth0) as a port to the Linux bridge. — A Linux bridge acts like a virtual switch. To allow the VM to reach the external network, the physical NIC (eth0) must be added as a port to the bridge. This bridges the VM's tap interface with the host's physical network, enabling Layer 2 connectivity to the corporate network and upstream routing.
What should I do if I get this 350-401 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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This 350-401 practice question is part of Courseiva's free Cisco 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 350-401 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.