The answer is that the multicast group is not reachable. When a VTEP shows an 'Init' status for a remote peer in the `show nve peers` output, it means the local VTEP has learned the remote IP address—typically through BGP EVPN or static configuration—but cannot complete the VXLAN tunnel establishment. In multicast-based VXLAN, the underlay multicast group is essential for BUM traffic forwarding and VTEP discovery; if the multicast group is unreachable due to missing PIM, an incorrect RP, or ACL filtering, the source VTEP cannot receive the necessary multicast join or data from the remote VTEP, leaving the peer stuck in 'Init'. On the Cisco DCCOR 350-601 exam, this scenario tests your understanding of VXLAN control and data plane dependencies, often appearing as a trap where candidates mistakenly suspect BGP EVPN misconfiguration instead of the underlay multicast issue. Remember the memory tip: "Init means the IP is known, but the multicast path is not grown."
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 network engineer is troubleshooting VXLAN connectivity between two VTEPs. The source VTEP is configured with `nve1` and member VNI 10000. The `show nve peers` command shows the remote VTEP IP but the status is 'Init'. What is a likely cause?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The multicast group is not reachable.
The 'Init' status in the output of 'show nve peers' indicates that the VXLAN tunnel endpoint (VTEP) has learned the remote VTEP IP address (likely via BGP EVPN or static configuration) but is unable to complete the tunnel establishment. In VXLAN multicast mode, the underlay multicast group is used for BUM traffic and for VTEP discovery. If the multicast group is not reachable (e.g., due to missing PIM configuration, incorrect RP, or firewall filtering), the source VTEP cannot receive the multicast join or data from the remote VTEP, leaving the peer stuck in 'Init' state.
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.
✓
The multicast group is not reachable.
Why this is correct
VXLAN relies on multicast for BUM traffic; if the multicast group is unreachable, the peer remains in 'Init'.
Related concept
Read the scenario before looking for a memorised answer.
✗
The remote VTEP is not configured with the same VNI.
Why it's wrong here
VNI mismatch would cause traffic drops but not necessarily keep the peer in 'Init' state; the peer could still be 'Up' with no VNI mapping.
✗
The MTU is too low.
Why it's wrong here
MTU issues cause fragmentation or drops, not peer state 'Init'.
✗
The VRF is mismatched between the VTEPs.
Why it's wrong here
VRF mismatch affects Layer 3 routing but does not prevent NVE peer establishment.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between control-plane and data-plane issues; the trap here is that candidates assume 'Init' means a configuration mismatch (like VNI or VRF) rather than an underlay multicast reachability problem, because they overlook that VXLAN multicast mode requires a functional underlay multicast tree for peer establishment.
Detailed technical explanation
How to think about this question
In VXLAN multicast mode, the underlay multicast group (e.g., 239.1.1.1) is used for BUM traffic and for VTEP auto-discovery via IGMP/MLD. The 'Init' state means the source VTEP has learned the remote VTEP's IP (e.g., via BGP EVPN Type-3 routes) but has not yet received a multicast join from that remote VTEP for the group, or the multicast data path is broken. A common real-world scenario is missing PIM sparse-mode configuration on the underlay routers or an incorrect RP mapping, causing the multicast tree to never form.
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 practitioner preparing for the 350-601 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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: The multicast group is not reachable. — The 'Init' status in the output of 'show nve peers' indicates that the VXLAN tunnel endpoint (VTEP) has learned the remote VTEP IP address (likely via BGP EVPN or static configuration) but is unable to complete the tunnel establishment. In VXLAN multicast mode, the underlay multicast group is used for BUM traffic and for VTEP discovery. If the multicast group is not reachable (e.g., due to missing PIM configuration, incorrect RP, or firewall filtering), the source VTEP cannot receive the multicast join or data from the remote VTEP, leaving the peer stuck in 'Init' state.
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
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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 VXLAN network where traffic between two VTEPs in the same VNI is not being forwarded. The underlay network is operational and IP connectivity exists between the VTEPs. Which two actions should the engineer take to verify the VXLAN configuration?
easy
A.Verify that the multicast group for BUM traffic is reachable.
✓ B.Verify that the NVE interface is configured with the correct source-interface.
C.Verify that the VXLAN tunnel endpoint IP addresses are in the same subnet.
✓ D.Verify that the VNI is mapped to the correct VLAN on the local VTEP.
E.Verify that the VXLAN routing table is populated correctly.
Why B: A and B are correct because the NVE interface must have a valid source-interface to encapsulate VXLAN packets, and the VNI must be mapped to the correct VLAN to forward traffic. Option C is incorrect because multicast group reachability is only required for BUM traffic, not unicast. Option D is incorrect because VTEP IPs can be on different subnets. Option E is incorrect because VXLAN is a Layer 2 overlay and does not involve routing.
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Question Discussion
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