The answer is that the BGP EVPN route table is missing the MAC/IP route for the destination. In a VXLAN EVPN fabric, when an ingress VTEP receives a frame destined for a known MAC address on a remote VTEP, it must perform a lookup in the BGP EVPN route table to find the corresponding MAC/IP route, which provides the mapping to the correct remote VTEP and its tunnel endpoint. If that specific MAC/IP route is absent—either because it was never advertised or was withdrawn—the ingress VTEP has no way to identify the target VTEP and is forced to flood the frame to all VTEPs in the VNI, explaining the observed behavior. On the Cisco DCCOR 350-601 exam, this scenario tests your understanding of the EVPN control plane versus data plane, with a common trap being to blame ARP suppression or STP. Remember the key: no MAC/IP route in the EVPN table means no remote VTEP mapping, so the switch falls back to flooding—think "no route, all flood."
350-601 Network Practice Question
This 350-601 practice question tests your understanding of network. 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.
A network engineer notices that when a host sends a packet to a destination on a different VTEP, the packet is flooded to all VTEPs even though the destination MAC is known. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The BGP EVPN route table is missing the MAC/IP route for the destination.
In a BGP EVPN VXLAN fabric, when a host sends a packet to a known destination MAC on a different VTEP, the ingress VTEP should perform MAC/IP route lookup in the BGP EVPN route table to determine the correct remote VTEP. If the MAC/IP route for the destination is missing (e.g., not advertised or withdrawn), the ingress VTEP has no mapping to a remote VTEP and must flood the packet to all VTEPs in the VNI, causing unnecessary broadcast traffic. This is the most likely cause of the described behavior.
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 BGP EVPN route table is missing the MAC/IP route for the destination.
Why this is correct
Without the route, the VTEP has no forwarding information and floods.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The VNI is misconfigured.
Why it's wrong here
VNI misconfiguration would cause connectivity failure, not flooding.
ARP suppression reduces broadcast ARP, not known unicast flooding.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse flooding due to an unknown MAC (which is normal) with flooding due to a missing EVPN route, or they incorrectly attribute the issue to ARP suppression or MTU problems, which are unrelated to the data-plane flooding of a known MAC across VTEPs.
Detailed technical explanation
How to think about this question
In BGP EVPN, the MAC/IP advertisement route (type-2) carries the MAC address, IP address, and VNI, and is used by VTEPs to build a forwarding table that maps MAC addresses to remote VTEPs. When a MAC is known locally but its corresponding EVPN type-2 route is missing (e.g., due to BGP session failure, route filtering, or silent host behavior), the ingress VTEP falls back to flooding within the VNI, as it has no remote VTEP target. This is often seen in scenarios where the destination host is a silent host that never sends traffic, so its MAC/IP route is never advertised, or when BGP route refresh is incomplete.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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 BGP EVPN route table is missing the MAC/IP route for the destination. — In a BGP EVPN VXLAN fabric, when a host sends a packet to a known destination MAC on a different VTEP, the ingress VTEP should perform MAC/IP route lookup in the BGP EVPN route table to determine the correct remote VTEP. If the MAC/IP route for the destination is missing (e.g., not advertised or withdrawn), the ingress VTEP has no mapping to a remote VTEP and must flood the packet to all VTEPs in the VNI, causing unnecessary broadcast traffic. This is the most likely cause of the described behavior.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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