Discuss Nokia 4A0-D03 Exam Topic 3 Question 2

Consider the exhibit.

All three of the leafs have a MP-BGP EVPN session to the route-reflector Spine-1. Leaf-1, Leaf-2 and Leaf-3 have existing instances of an L2 EVPN named MAC VRF-1. Host-1 has just sent its first Ethernet frame into MAC VRF-1 on Leaf-1.

Which of the following steps is FALSE?

ALeaf-1 populates Host-1's MAC address learnt on the local interface to its MAC table.

BLeaf-1 generates an EVPN route-type 5 update with Host-1's MAC address and sends it to the route reflector.

CThe route-reflector forwards the EVPN update to Leaf-2 and Leaf-3.

DLeaf-2 and Leaf-3 import the EVPN update based upon the route target.

Suggested Answer: B

Comprehensive and Detailed 150 to 250 words of Explanation From [SR Linux EVPN and Data Center Interconnect/Course Guide/topics]:

When Host-1 sends its first Ethernet frame into MAC VRF-1, Leaf-1 performs normal local data-plane MAC learning on the access interface and installs Host-1's MAC address into the MAC forwarding table. In an L2 EVPN MAC-VRF, host MAC reachability is then advertised into the EVPN control plane using EVPN route type 2, the MAC/IP Advertisement route. Route type 5 is not used for host MAC advertisement; RT-5 is used for IP prefix advertisement in Layer 3 EVPN services. Therefore, option B is false because it incorrectly states that Leaf-1 generates an EVPN RT-5 update with the host MAC address. In this topology, Leaf-1 sends the correct EVPN update to the route reflector, Spine-1. The route reflector then reflects the update to Leaf-2 and Leaf-3, and those remote leaves import the route if the route target matches their MAC VRF-1 import policy. The route target controls service membership, ensuring that only PEs participating in the same EVPN instance import the MAC route. Reference: L2 EVPN MAC learning, RT-2 MAC/IP advertisement, route-reflector distribution, route-target import.

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12 comments · newest first

Walker 1 month ago

No way, B is correct. Leaf-1 must send the update after learning the MAC.

Shaun 2 months ago

I agree, but I feel like option B could be misleading too.

Tresa 2 months ago

I think option A is false. Leaf-1 should learn the MAC address first.

Odette 2 months ago

All steps seem legit, but I’m not sure about D.

Phil 2 months ago

Wait, why would Leaf-2 and Leaf-3 need to import it?

Tamesha 2 months ago

C makes sense, route-reflectors do that.

Cyril 2 months ago

I think B is the false one, seems off to me.

Elmer 3 months ago

Leaf-1 definitely populates the MAC address in its table.

Becky 3 months ago

I feel like Leaf-2 and Leaf-3 importing the update based on route target could be a trick option. I need to double-check how that works.

Gladys 3 months ago

I practiced a similar question where the route reflector's role was emphasized. I think it does forward updates to other leaves, so that part seems correct.

Theola 3 months ago

I'm a bit unsure about the EVPN route-type 5 update. I remember something about it, but I can't recall if Leaf-1 sends that immediately.

Candida 3 months ago

I think Leaf-1 definitely populates the MAC address in its table, that seems straightforward.

Nokia 4A0-D03 Exam - Topic 3 Question 2 Discussion