How Can EPG-12 and EPG-10 Share VLAN-12 on the Same ACI Leaf?
Short answer
B Enable port-local VLAN scope on the Leaf-101 and Leaf-102 ports so EPG-12 can reuse the VLAN-12 encapsulation already used by EPG-10.
Question
Key Takeaways
It tests ACI's rule for duplicate VLAN encapsulation on one leaf: the EPGs need different bridge domains, different ports, and port-local VLAN scope.
Two ACI EPGs, EPG-10 and EPG-12, can reuse VLAN-12 encapsulation on Leaf-101 and Leaf-102 only after port-local VLAN scope is enabled. This page confirms port-local VLAN scope (B) as the required step for SVR-12 connectivity.
Common mistake: The tempting wrong answer is A — placing EPG-12 in the same BD as EPG-10; Cisco instead requires EPGs that share an encapsulation to use different bridge domains.
Expert Analysis
Why the Answer Is Correct
In Cisco ACI, a VLAN encapsulation is normally unique per leaf switch, so EPG-12 and EPG-10 both using VLAN-12 on Leaf-101 and Leaf-102 would conflict by default. Cisco's Layer 2 configuration guide states that to deploy multiple EPGs with the same encapsulation on a single leaf, the EPGs must be associated with different bridge domains, deployed on different ports, tied to the same domain/VLAN pool containing that VLAN, and the ports must be configured with port-local VLAN scope. SVR-12 lands on port-12 while SVR-10 uses other ports, so enabling port-local VLAN scope on those leaf ports is exactly what allows VLAN-12 to be reused. Option B therefore resolves the encapsulation collision without changing the VLAN pool or the fabric-wide VLAN policy.
Why the Other Options Are Wrong
Option A is the opposite of the Cisco rule: sharing the same bridge domain between EPG-12 and EPG-10 is precisely what is disallowed when both EPGs use the same encapsulation on one leaf, because overlapping subnets and forwarding domains would collide. Option C is irrelevant, since native VLAN is a trunk/untagged-frame concept and does not control ACI EPG encapsulation uniqueness. Option D addresses IP addressing, but ACI forwards traffic based on EPG and BD context, not on subnet membership, so moving SVR-12 to another subnet would not remove the duplicate VLAN-12 conflict on the leaf ports.
Community Comment Notes
As prospio971 explained, the conflict exists because ACI by default forbids the same VLAN encapsulation for multiple EPGs on the same port or leaf, and port-local VLAN scope is the fix. ed27 quoted the Cisco guidelines directly, including "EPGs must be associated with different bridge domains" and "Ports must be configured with portLocal VLAN sco", which rules out option A and supports B. zelya19 also pointed to the official Cisco L2 networking configuration guide page for EPGs, and designated simply agreed that B is correct. The learner vote record here is unanimous for B, which matches the documented ACI behavior.
Official Reference
This link opens the official vendor documentation in a new tab.
Exam Strategy
When two ACI EPGs reuse one VLAN encapsulation, immediately look for the port-local VLAN scope requirement rather than a bridge-domain or IP change. Memorize the trio of conditions Cisco lists — different BDs, different ports, same VLAN-pool domain — and verify the port-level setting before answering.
Frequently Asked Questions
Why can't EPG-12 use the same bridge domain as EPG-10 when both use VLAN-12?
Does disabling the native VLAN solve the duplicate VLAN-12 encapsulation conflict?
Community Votes
100% of anonymous learners picked answer B. Votes are pick records left by other test-takers — they are not the verified answer.
Discussion 4 contributions
Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.
From public community threads 4
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ed27 👍 1 Answered BTo enable deploying multiple EPGs using the same encapsulation number, on a single leaf switch, use the following guidelines: EPGs must be associated with different bridge domains. EPGs must be deployed on different ports. Both the port and EPG must be associated with the same domain that is associated with a VLAN pool that contains the VLAN number. Ports must be configured with portLocal VLAN scope.
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prospio971 👍 1 Answered BIn Cisco ACI, when two EPGs (e.g., EPG-10 and EPG-12) need to use the same VLAN encapsulation (VLAN-12) on the same leaf switch (Leaf-101 and Leaf-102), a conflict arises because ACI by default does not allow the same VLAN encapsulation to be used for multiple EPGs on the same port or leaf. To resolve this, port local VLAN scope must be enabled.
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zelya19 👍 1 Answered Bhttps://www.cisco.com/c/en/us/td/docs/dcn/aci/apic/6x/l2-configuration/cisco-apic-layer-2-networking-configuration-guide-60x/epgs-60x.html#concept_BC396E1CBB7D4687A9CBBECDDD43DE11
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designated 👍 1 Answered BB is correct
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