Quick Answer
The answer is LISP, or the Locator/ID Separation Protocol, because it decouples a wireless endpoint’s identity (EID) from its location (RLOC), allowing seamless roaming across fabric edge nodes in an SD-Access campus. In the fabric, LISP maintains a centralized mapping database that tracks where each wireless client is attached, so traffic is forwarded to the correct edge node without requiring re-anchoring or tunnel reconfiguration as the client moves between access points. On the ENCOR 350-401 exam, this question tests your understanding of how SD-Access handles wireless mobility without traditional controllers—a common trap is confusing LISP with VXLAN or OTV, but remember that VXLAN handles data-plane encapsulation while LISP manages the control-plane mapping for endpoint mobility. A helpful memory tip: think of LISP as the “phonebook” for wireless clients—it looks up where they are (RLOC) by their name (EID), so they can roam freely without losing their connection.
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.
An architect is designing an SD-Access fabric for a campus with multiple buildings. The design must support wireless clients seamlessly roaming across fabric edge nodes. Which technology is used in the fabric to provide mobility for wireless endpoints?
LISP
LISP handles endpoint mobility by updating the EID-to-RLOC mapping when a client roams.
VXLAN
Why wrong: VXLAN is the data plane encapsulation but does not handle mobility control.
OTV
Why wrong: OTV is used for Layer 2 extension between data centers, not for fabric mobility.
MPLS
Why wrong: MPLS is not used for endpoint mobility in SD-Access.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
LISP
LISP (Locator/ID Separation Protocol) is the correct technology because it decouples the endpoint identifier (EID) from its routing locator (RLOC), enabling seamless roaming across fabric edge nodes. In SD-Access, LISP maintains a mapping database that tracks wireless endpoint locations, allowing traffic to be forwarded to the correct fabric edge without re-anchoring or tunneling changes as clients move between access points.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
LISP
Why this is correct
LISP handles endpoint mobility by updating the EID-to-RLOC mapping when a client roams.
Related concept
Read the scenario before looking for a memorised answer.
VXLAN
Why it's wrong here
VXLAN is the data plane encapsulation but does not handle mobility control.
OTV
Why it's wrong here
OTV is used for Layer 2 extension between data centers, not for fabric mobility.
MPLS
Why it's wrong here
MPLS is not used for endpoint mobility in SD-Access.
Common exam traps
Cisco often tests the misconception that VXLAN alone handles mobility, but the trap here is that VXLAN is only the data-plane encapsulation; LISP is the control-plane protocol that actually enables endpoint tracking and seamless roaming in SD-Access.
Detailed technical explanation
LISP uses a mapping system with Map-Server (MS) and Map-Resolver (MR) to maintain EID-to-RLOC bindings; when a wireless client roams to a new fabric edge, the edge sends a Map-Register update to the MS, and the MS notifies other edges via Map-Notify, ensuring traffic is redirected without flooding. In real-world deployments, this allows sub-second roaming convergence because the control plane updates occur before the client’s traffic is disrupted, avoiding the need for traditional ARP or MAC learning across the fabric.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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.
What to study next
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FAQ
SD-Access Architecture — This question tests SD-Access Architecture — Read the scenario before looking for a memorised answer..
The correct answer is: LISP — LISP (Locator/ID Separation Protocol) is the correct technology because it decouples the endpoint identifier (EID) from its routing locator (RLOC), enabling seamless roaming across fabric edge nodes. In SD-Access, LISP maintains a mapping database that tracks wireless endpoint locations, allowing traffic to be forwarded to the correct fabric edge without re-anchoring or tunneling changes as clients move between access points.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
About these practice questions
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Same concept, more angles
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which two statements about LISP in Cisco SD-Access are true? (Choose two.)
mediumWhy A: LISP (Locator/ID Separation Protocol) is the control plane in SD-Access. The Map Server (MS) maintains the EID-to-RLOC mapping database, and the Map Resolver (MR) handles Map-Request queries. The EID represents the endpoint identity (IP address), while the RLOC is the routing locator (IP address of the fabric node). LISP does not perform encapsulation; VXLAN does. LISP uses UDP ports 4342 (data plane) and 4341 (control plane), not TCP. The EID is typically the host IP, not the MAC address.
Variation 2. An architect is planning a Cisco SD-Access fabric deployment. The design must support host mobility across multiple fabric edge nodes while ensuring consistent policy enforcement. Which fabric component is responsible for tracking endpoint locations and mapping them to the fabric?
mediumWhy A: In Cisco SD-Access, the fabric control plane node (based on LISP) is responsible for maintaining the endpoint database (EID-to-RLOC mappings). When a host moves between fabric edge nodes, the control plane node updates the mapping, ensuring consistent policy enforcement by providing the correct location information to all edge nodes.
Last reviewed: Jun 24, 2026
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