The answer is that EVPN multihoming aliasing enables one PE to advertise MAC addresses for another PE in the same Ethernet Segment. This is correct because in all-active multihoming, remote PEs need to know they can reach a given MAC address through any of the multihomed PEs for load balancing; aliasing allows a PE that has locally learned a MAC to advertise that MAC on behalf of its peer PEs, effectively creating multiple equal-cost paths to the same MAC. On the Cisco SPCOR / CCNP Service Provider Core 350-501 exam, this concept tests your understanding of how EVPN avoids the “designated forwarder” bottleneck in all-active mode—a common trap is confusing aliasing with the DF election process, which handles BUM traffic, not unicast load balancing. Remember the memory tip: “Aliasing = Advertising for a buddy,” meaning one PE speaks for another to spread traffic across the segment.
350-501 Services Practice Question
This 350-501 practice question tests your understanding of services. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
In EVPN multihoming with all-active mode, what is the purpose of the aliasing capability?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
It enables one PE to advertise MAC addresses for another PE in the same ES.
In EVPN all-active multihoming, the aliasing capability allows a PE that has learned a MAC address via local attachment to the Ethernet Segment (ES) to advertise that MAC address on behalf of other PEs in the same ES. This enables remote PEs to load-balance traffic destined to that MAC across all multihomed PEs, even if only one PE actually learned the MAC locally. Without aliasing, traffic would be forced to the specific PE that learned the MAC, defeating the purpose of all-active redundancy.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
It permits the use of a single ESI label across all PEs in the ES.
Why it's wrong here
Incorrect. ESI labels are used for split-horizon and are per PE, not shared.
✗
It reduces the number of BGP updates by aggregating MAC routes.
Why it's wrong here
Incorrect. Aliasing may actually increase updates because each PE advertises additional MAC routes.
✗
It allows load balancing of traffic across all PEs.
Why it's wrong here
Incorrect. Load balancing is a result of aliasing, but the specific purpose is to advertise MACs on behalf of other PEs.
✓
It enables one PE to advertise MAC addresses for another PE in the same ES.
Why this is correct
Correct. Aliasing allows a PE to advertise MACs for other PEs in the same ES, making all active paths known.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between aliasing (advertising MACs for other PEs) and load balancing (the forwarding behavior that aliasing enables), causing candidates to mistakenly select 'load balancing' as the purpose of aliasing itself.
Detailed technical explanation
How to think about this question
Under the hood, aliasing is implemented via the EVPN MAC/IP Advertisement route (type 2) where a PE includes the ESI of the multihomed segment. When a remote PE receives multiple type 2 routes for the same MAC address from different PEs in the same ES, it installs multiple equal-cost next hops, enabling per-flow load balancing. In real-world scenarios, this is critical for active-active LACP configurations where hosts may send traffic to any PE, and aliasing ensures that return traffic can be balanced across all PEs without requiring MAC mobility or ARP suppression issues.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Services — This question tests Services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: It enables one PE to advertise MAC addresses for another PE in the same ES. — In EVPN all-active multihoming, the aliasing capability allows a PE that has learned a MAC address via local attachment to the Ethernet Segment (ES) to advertise that MAC address on behalf of other PEs in the same ES. This enables remote PEs to load-balance traffic destined to that MAC across all multihomed PEs, even if only one PE actually learned the MAC locally. Without aliasing, traffic would be forced to the specific PE that learned the MAC, defeating the purpose of all-active redundancy.
What should I do if I get this 350-501 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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