The correct action is to verify that the new leaf has the address-family l2vpn evpn activated under the neighbor configuration. This is because, in BGP EVPN, simply enabling the address-family globally under router bgp does not instruct the router to advertise prefixes to a specific peer; the address-family must be explicitly activated under the neighbor statement for the session to exchange EVPN routes. On the Cisco DCCOR and CCNP Data Center Core 350-601 exam, this is a classic troubleshooting scenario where a BGP session is up but routes are missing, testing your understanding that neighbor-level address-family activation is separate from global configuration. A common trap is assuming a global address-family configuration is sufficient, but without the neighbor activation, the spine route reflectors receive no routes from the new leaf to propagate. Remember the memory tip: “Global enables the engine, neighbor activates the gear”—you need both for routes to move.
350-601 Network Practice Question
This 350-601 practice question tests your understanding of network. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
A data center runs OSPF as the underlay for an EVPN-VXLAN fabric. The fabric includes two spine switches and eight leaf switches. After adding a new leaf switch, the network team notices that some EVPN routes are missing from the other leaves. The new leaf has established BGP EVPN sessions to both spines and the BGP sessions are up. The spines report receiving all routes from the new leaf, but the other leaves do not receive certain prefixes. The engineer checks the BGP configuration on the new leaf and sees the address-family l2vpn evpn is configured under router bgp. Which action should the engineer take to resolve the issue?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Verify the new leaf has the address-family l2vpn evpn activated under the neighbor configuration
The issue is that the new leaf has BGP EVPN sessions to both spines, but other leaves do not receive certain prefixes. Since the spines (acting as route reflectors) receive all routes from the new leaf but do not propagate them to other leaves, the most likely cause is that the address-family l2vpn evpn is not activated under the neighbor configuration on the new leaf. Without this activation, the new leaf does not advertise its EVPN routes to the spines, even though the BGP session is up and the address-family is configured globally under router bgp.
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.
✗
Check the new leaf's BGP router ID for uniqueness
Why it's wrong here
Duplicate router ID would cause warnings but not missing routes.
✓
Verify the new leaf has the address-family l2vpn evpn activated under the neighbor configuration
Why this is correct
The address-family must be activated under each neighbor to advertise routes.
Related concept
Read the scenario before looking for a memorised answer.
✗
Ensure the new leaf's BGP next-hop-self is enabled
Why it's wrong here
Next-hop-self is typically applied on route reflectors, not leaves.
✗
Verify the cluster ID on the route reflectors is consistent
Why it's wrong here
Cluster ID mismatch does not affect route exchange when sessions are up.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between configuring the address-family globally under router bgp versus activating it under a specific neighbor, leading candidates to assume global configuration is sufficient.
Detailed technical explanation
How to think about this question
In BGP EVPN, the address-family l2vpn evpn must be explicitly activated under each neighbor using the 'neighbor X.X.X.X activate' command in the address-family configuration mode. Without this, the BGP session may be established for other address families (e.g., IPv4 unicast) but EVNL routes are not exchanged. This is a common misconfiguration when adding a new leaf, as the global address-family configuration does not automatically apply to all neighbors.
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 network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
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.
Network — This question tests Network — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Verify the new leaf has the address-family l2vpn evpn activated under the neighbor configuration — The issue is that the new leaf has BGP EVPN sessions to both spines, but other leaves do not receive certain prefixes. Since the spines (acting as route reflectors) receive all routes from the new leaf but do not propagate them to other leaves, the most likely cause is that the address-family l2vpn evpn is not activated under the neighbor configuration on the new leaf. Without this activation, the new leaf does not advertise its EVPN routes to the spines, even though the BGP session is up and the address-family is configured globally under router bgp.
What should I do if I get this 350-601 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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. An engineer is troubleshooting a BGP EVPN session between a leaf and a spine. The 'show bgp l2vpn evpn summary' output shows the peer state as 'Active'. What does this indicate?
medium
A.The session is in the process of being established.
B.The session is up and exchanging prefixes.
C.There is a configuration mismatch.
✓ D.The TCP connection is not established.
Why D: In BGP EVPN, the 'Active' state indicates that the BGP speaker is actively trying to establish a TCP connection with the peer but has not yet completed the three-way handshake. This means the TCP session is not established, which is a prerequisite for BGP session establishment. The peer remains in 'Active' until the TCP connection is successfully formed.
Last reviewed: Jun 24, 2026
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