An engineer is investigating an EVPN traffic flow issue. Which type of traffic should the engineer allow in an EVPN Tree Service in order to fix this issue?

Question

Options

• Aknown unicast from a leaf to another leaf
• Bunknown unicast from a leaf to another leaf
• Cmulticast from a leaf to another leaf
• Dknown unicast from a root to another root

• A
  6% (1)
• B
  11% (2)
• C
  6% (1)
• D
  78% (14)

Explanation

In an EVPN E-Tree (Tree) Service, the fundamental topology rule is that root sites can communicate with all other sites (roots and leaves), while leaf sites can only communicate with root sites - never with other leaves. Allowing known unicast from root to root (option D) is the correct traffic type to permit because it aligns with the E-Tree service model, where root-to-root forwarding must be explicitly enabled to restore proper traffic flow.

Why the distractors are wrong:

• A & B (leaf-to-leaf unicast): E-Tree specifically prohibits leaf-to-leaf traffic - that is the defining purpose of the service. Allowing this would break the topology contract, not fix it.
• C (multicast from leaf to leaf): Same reason - leaf isolation applies to all traffic types, including multicast.
• D is correct because root nodes are "privileged" endpoints in E-Tree and must be able to exchange known unicast traffic with each other for the service to function.

Memory tip: Think of an actual tree - the roots are at the base and are interconnected, while the leaves only attach to branches/roots and never directly to each other. In EVPN E-Tree, traffic follows the same rule: leaves talk up, roots talk everywhere.

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