Nokia SR Linux EVPN and Data Center Interconnect 4A0-D03 Question # 10 Topic 2 Discussion
4A0-D03 Exam Topic 2 Question 10 Discussion:
Question #: 10
Topic #: 2
When providing L3 multi-homing on two or more leaf routers, which of the following is FALSE?
A.
In a single-active multi-homing scenario, the DF-election is used to identify the active leaf router.
B.
In an all-active multi-homing scenario, the DF-election is used to identify the leaf router that is responsible for forwarding BUM traffic to the host.
C.
All learned 3rd party prefixes are advertised using EVPN route type 5.
D.
The Ethernet segment is associated with the next-hop for the 3rd party prefixes.
Comprehensive and Detailed 150 to 250 words of Explanation From [SR Linux EVPN and Data Center Interconnect/Course Guide/topics]:
Layer 3 multi-homing is fundamentally about redundant or load-balanced L3 reachability for external prefixes, not about Layer 2 broadcast-domain flooding toward a host. In single-active L3 multi-homing, DF election determines which attached leaf is active for the Ethernet Segment, and only that leaf advertises or forwards for the attached customer route as required by the redundancy model. In all-active L3 multi-homing, multiple leaf routers can be valid next-hops for the same learned third-party prefix, and remote PEs may load-balance toward them based on the Ethernet Segment association. Learned external prefixes are carried as EVPN route type 5 IP Prefix routes, which is the correct route type for L3 reachability. The Ethernet Segment is associated with the next-hop for those prefixes so that remote PEs understand the multi-homed nature of the path. Option B is false because BUM forwarding is a Layer 2 EVPN concern. In an all-active L3 multi-homing scenario, DF election is not used to identify a BUM-forwarding leaf for host traffic in the same way it is used in Layer 2 multi-homing services. Reference: L3 EVPN multi-homing, RT-5 prefix routes, ES next-hop behavior.
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