The answer is the fabric border node. This role is correct because it serves as the gateway between the SD-Access fabric and external networks, performing Network-to-Network Interconnection (NNI) to translate VXLAN-encapsulated traffic into the appropriate WAN transport such as IPsec or MPLS. By aggregating inter-site traffic at the border, it eliminates the need for a full mesh of VXLAN tunnels between all edge nodes, reducing tunnel overhead and simplifying the fabric architecture for inter-site connectivity without full mesh VXLAN. On the ENCOR 350-401 exam, this concept tests your understanding of SD-Access fabric roles and WAN integration, often appearing in design scenario questions where a common trap is confusing the border node with the control plane node or edge node. Remember: the border node is the fabric’s “exit door” to the outside world, so think “border = boundary to WAN” to avoid mixing it up with internal fabric roles.
350-401 SD-Access Architecture Practice Question
This 350-401 practice question tests your understanding of sd-access architecture. 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.
A company is deploying an SD-Access fabric with multiple sites connected via a WAN. The design must allow inter-site traffic to be forwarded without requiring a full mesh of VXLAN tunnels between all edge nodes. Which fabric role should be used to interconnect the sites?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Fabric border node
A Fabric Border Node is the correct role because it acts as the gateway between the SD-Access fabric and external networks, including WAN connections. It performs Network-to-Network Interconnection (NNI) by translating VXLAN-encapsulated traffic into the appropriate WAN transport (e.g., IPsec, MPLS) and handles inter-site routing without requiring a full mesh of VXLAN tunnels between all Edge Nodes. This design leverages the Border Node to aggregate traffic and forward it over the WAN, reducing tunnel overhead and simplifying the fabric architecture.
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.
✓
Fabric border node
Why this is correct
Border nodes act as the gateway between the fabric and external networks, enabling inter-site connectivity.
Related concept
Read the scenario before looking for a memorised answer.
✗
Fabric control plane node
Why it's wrong here
Control plane nodes manage endpoint mappings but do not forward inter-site traffic.
✗
Fabric edge node
Why it's wrong here
Edge nodes connect endpoints but are not designed for inter-site routing.
✗
Fabric WAN controller
Why it's wrong here
There is no dedicated fabric WAN controller in SD-Access; border nodes handle WAN connectivity.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that a Fabric Edge Node can directly forward traffic between sites, but the trap here is that Edge Nodes only handle intra-site VXLAN tunnels and rely on Border Nodes for any traffic leaving the fabric site.
Detailed technical explanation
How to think about this question
In Cisco SD-Access, the Fabric Border Node performs inter-site routing by decapsulating VXLAN traffic from the local fabric, applying any necessary policy (e.g., SGT mapping), and re-encapsulating it into the WAN transport (e.g., IPsec/GRE). This design uses a hub-and-spoke model where each site's Border Node connects to a central WAN or to other Border Nodes via a single tunnel, avoiding the O(N^2) tunnel scaling issue of a full mesh. Under the hood, the Border Node can also function as a Control Plane Node (collapsed role) for smaller deployments, but its primary inter-site function relies on LISP for location mapping and VXLAN for data encapsulation.
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 practitioner preparing for the 350-401 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 350-401 question in full detail.
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: Fabric border node — A Fabric Border Node is the correct role because it acts as the gateway between the SD-Access fabric and external networks, including WAN connections. It performs Network-to-Network Interconnection (NNI) by translating VXLAN-encapsulated traffic into the appropriate WAN transport (e.g., IPsec, MPLS) and handles inter-site routing without requiring a full mesh of VXLAN tunnels between all Edge Nodes. This design leverages the Border Node to aggregate traffic and forward it over the WAN, reducing tunnel overhead and simplifying the fabric architecture.
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.
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Question Discussion
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