Question 2,011 of 2,015

SD-Access Architecture →mediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is a misconfiguration of the anycast gateway feature on the fabric edge node. In Cisco SD-Access, the anycast gateway is not automatically active when you create a VLAN SVI; it requires explicit configuration under the interface, including commands like `ip virtual-reassembly` and `ip local-proxy-arp`, along with the `anycast-gateway` keyword. Without these, the fabric edge cannot respond to ARP requests for the virtual default gateway IP, even if the SVI exists, breaking all Layer 3 connectivity for users in that VLAN. On the ENCOR 350-401 exam, this scenario tests your understanding that SD-Access anycast gateway configuration is a deliberate, multi-step process—not a default behavior—and a common trap is assuming an SVI alone provides gateway services. Remember the mnemonic “SVI is not enough; you must flip the anycast switch” to recall that the feature must be explicitly enabled for the fabric edge to act as the default gateway.

350-401 SD-Access Architecture Practice Question

This 350-401 practice question tests your understanding of sd-access architecture. 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 enterprise is migrating from a traditional three-tier campus network to Cisco SD-Access. The network engineer has deployed a fabric with a single fabric edge node and a single control plane node. Users in VLAN 10 report that they cannot reach the default gateway, which is a virtual IP on the fabric edge. The fabric edge is configured with a VLAN 10 SVI and the anycast gateway feature is enabled. What is the most likely cause of the problem?

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.

Question 1mediummultiple choice

Open the full VLAN trunking answer →

A
The fabric edge node is not configured with the VLAN 10 SVI or the anycast gateway feature is disabled.
Correct. Without the SVI and anycast gateway enabled, the fabric edge cannot provide the default gateway for VLAN 10 users.
B
The control plane node is not reachable from the fabric edge, causing the fabric edge to drop traffic.
Why wrong: Incorrect. While the control plane node is needed for endpoint registration, the fabric edge can still forward traffic locally. The default gateway issue is more fundamental.
C
The endpoints are not configured with the correct IP address for the default gateway.
Why wrong: Incorrect. The scenario states users cannot reach the default gateway, implying the gateway itself is not responding, not that the endpoints have wrong IPs.
D
The fabric edge node is in Layer 2 mode and cannot route traffic.
Why wrong: Incorrect. Even in Layer 2 mode, the fabric edge can have an SVI and provide routing. The anycast gateway feature works in both modes.

Full breakdown with real-world context →

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

The fabric edge node is not configured with the VLAN 10 SVI or the anycast gateway feature is disabled.

Option A is correct because the question states that the fabric edge is configured with a VLAN 10 SVI and anycast gateway is enabled, yet users cannot reach the default gateway. The most likely cause is a misconfiguration: either the SVI is missing or anycast gateway is disabled on the fabric edge. In Cisco SD-Access, the anycast gateway feature must be explicitly enabled under the SVI using the command 'ip virtual-reassembly in' and 'ip local-proxy-arp' along with the 'anycast-gateway' configuration; without it, the fabric edge cannot respond to ARP requests or route traffic for the virtual IP, breaking connectivity to the default gateway.

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 fabric edge node is not configured with the VLAN 10 SVI or the anycast gateway feature is disabled.
Why this is correct
Correct. Without the SVI and anycast gateway enabled, the fabric edge cannot provide the default gateway for VLAN 10 users.
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.
✗
The control plane node is not reachable from the fabric edge, causing the fabric edge to drop traffic.
Why it's wrong here
Incorrect. While the control plane node is needed for endpoint registration, the fabric edge can still forward traffic locally. The default gateway issue is more fundamental.
✗
The endpoints are not configured with the correct IP address for the default gateway.
Why it's wrong here
Incorrect. The scenario states users cannot reach the default gateway, implying the gateway itself is not responding, not that the endpoints have wrong IPs.
✗
The fabric edge node is in Layer 2 mode and cannot route traffic.
Why it's wrong here
Incorrect. Even in Layer 2 mode, the fabric edge can have an SVI and provide routing. The anycast gateway feature works in both modes.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the misconception that anycast gateway is automatically enabled when an SVI is created on a fabric edge, but in reality it requires explicit configuration, and candidates may overlook this step when troubleshooting connectivity to the default gateway.

Trap categories for this question

Scenario analysis trap
Incorrect. The scenario states users cannot reach the default gateway, implying the gateway itself is not responding, not that the endpoints have wrong IPs.

Detailed technical explanation

How to think about this question

In Cisco SD-Access, the anycast gateway feature relies on the fabric edge node advertising the same virtual IP (e.g., 192.168.10.1) via LISP to the control plane, and it uses a unique anycast MAC address (typically 0000.0c9f.f000) to enable seamless host mobility. The SVI must have 'ip local-proxy-arp' enabled and the 'anycast-gateway' command applied under the VLAN configuration; without these, the fabric edge will not respond to ARP requests for the virtual IP, causing endpoints to fail to reach the default gateway even if the SVI exists. In a real-world migration, engineers often forget to enable anycast gateway after creating the SVI, leading to this exact issue.

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 help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.

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.

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FAQ

Questions learners often ask

What does this 350-401 question test?

SD-Access Architecture — This question tests SD-Access Architecture — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The fabric edge node is not configured with the VLAN 10 SVI or the anycast gateway feature is disabled. — Option A is correct because the question states that the fabric edge is configured with a VLAN 10 SVI and anycast gateway is enabled, yet users cannot reach the default gateway. The most likely cause is a misconfiguration: either the SVI is missing or anycast gateway is disabled on the fabric edge. In Cisco SD-Access, the anycast gateway feature must be explicitly enabled under the SVI using the command 'ip virtual-reassembly in' and 'ip local-proxy-arp' along with the 'anycast-gateway' configuration; without it, the fabric edge cannot respond to ARP requests or route traffic for the virtual IP, breaking connectivity to the default gateway.

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.

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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