The answer is that the load-balancing method is set to src-dst-ip, and all traffic is between the same two IP addresses. This causes an EtherChannel load balancing uneven single flow because the hash algorithm, when using source and destination IP, produces the same result for every packet in that conversation, forcing all traffic onto one physical link. On the ENCOR 350-401 exam, this scenario tests your understanding that EtherChannel load balancing is per-flow, not per-packet, and that identical source-destination pairs will never be distributed across multiple links, even when the port-channel is fully operational. A common trap is assuming a misconfiguration like mismatched port speeds or VLAN mismatches, but those would prevent the channel from coming up entirely. Remember the key insight: the hash is deterministic for a given flow, so a single flow cannot be split. Memory tip: “One flow, one link—same IP pair, same hash, same fate.”
CCNP EtherChannel Practice Question
This 350-401 practice question tests your understanding of etherchannel. 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 an EtherChannel between two Cisco switches. The show etherchannel 1 port-channel command shows the port-channel is up, but traffic is not load-balanced evenly. The engineer notices that all traffic is using only one link. The physical ports are all configured identically. 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 load-balancing method is set to src-dst-ip, and all traffic is between the same two IP addresses.
The correct answer is that the load-balancing method is set to src-dst-ip, but the traffic is from a single source to a single destination IP. The wrong answers involve issues that would prevent the channel from being up or affect all links.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 load-balancing method is set to src-mac, and the traffic is from multiple MAC addresses.
Why it's wrong here
Incorrect because src-mac would use multiple links if multiple source MACs are present.
✓
The load-balancing method is set to src-dst-ip, and all traffic is between the same two IP addresses.
Why this is correct
Correct because src-dst-ip hashes on source and destination IP; if they are the same, all traffic goes to the same link.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
The physical ports have different speeds.
Why it's wrong here
Incorrect because speed mismatch would cause some ports to be down, but the channel is up.
✗
The port-channel is configured with 'lacp fast-switchover'.
Why it's wrong here
Incorrect because fast-switchover affects failover, not load balancing.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 350-401 NAT questions on configuration and troubleshooting.
EtherChannel — This question tests EtherChannel — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The load-balancing method is set to src-dst-ip, and all traffic is between the same two IP addresses. — The correct answer is that the load-balancing method is set to src-dst-ip, but the traffic is from a single source to a single destination IP. The wrong answers involve issues that would prevent the channel from being up or affect all links.
What should I do if I get this 350-401 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 350-401 NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
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