VXLAN EVPN VNI to Multicast Group Mapping Methods
An engineer is building a data center network with VXLAN EVPN. The requirement is to use multicast for the broadcast, unknown unicast, and multicast replication. Which two VNI to multicast group mapping methods must be used to meet these requirements? (Choose two.)
Community Votes
100% of anonymous learners picked answer BC. Votes are pick records left by other test-takers — they are not the verified answer.
Community Insight
Tests knowledge of VXLAN EVPN scaling techniques where multiple Virtual Network Identifiers (VNIs) share a single multicast group, alongside the standard one-to-one mapping.
This question addresses VXLAN EVPN scalability using multicast for BUM traffic replication. It establishes that mapping many VNIs to a single multicast group and one VNI to one multicast group are the required methods.
Learners often select 'one VNI to one multicast group' twice or confuse NVE mappings with VNI mappings, failing to recognize the 'many-to-one' scaling strategy.
Community Discussion (4 comments)
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Expert Analysis
Why the Answer Is Correct
The correct options are B and C. In VXLAN EVPN deployments, especially in large-scale environments, managing a unique multicast group for every VNI is inefficient. The protocol supports two primary mapping strategies: 'One VNI to One Multicast Group' (Option B), which is the default and simplest method, and 'Many VNIs to One Multicast Group' (Option C), which is used for scaling by grouping similar traffic into a shared multicast tree. Both are valid and necessary methods to meet diverse network requirements.Why the Other Options Are Wrong
Options A and D focus on NVEs rather than VNIs, which misinterprets the question's requirement for VNI-to-multicast mapping. Option E suggests 'Many VNIs to Many Multicast Groups,' which describes a complex mesh that isn't a standard defined mapping method for this context. The core concepts tested are the specific ratios allowed by the standard.Community Comment Notes
Community consensus strongly supports BC. As user k3rnelpanicpj noted, "NVE is network virtual interface... exist only one. VNI can be mapped to multicast group in manner: 1 VNI:1 MCastGroup Many VNI: 1McastGroup." This highlights the distinction between the encapsulation endpoint (NVE) and the logical tenant identifier (VNI). Another user lurker8000 confirmed the logic, stating they were "going with B and C" based on the phrasing of the question.Exam Strategy
When studying VXLAN EVPN, always distinguish between the physical/logical endpoints (NVEs) and the logical networks (VNIs). Remember that scalability often comes from sharing resources, so look for 'many-to-one' relationships in scaling scenarios.
Frequently Asked Questions
Why is 'many NVE to one multicast group' incorrect?
The question asks for VNI-to-multicast mappings, not NVE mappings. NVEs are the endpoints, while VNIs are the logical networks being mapped to groups.
What is the benefit of 'many VNIs to one multicast group'?
It significantly reduces the number of multicast groups needed in the underlay network, improving scalability and reducing control plane overhead.