Question 1,539 of 1,389
CCNA Switching and Network Access Practice Question
Exhibit
SW1# show etherchannel load-balance
EtherChannel Load-Balancing Configuration:
src-mac
EtherChannel Load-Balancing Addresses Used Per-Protocol:
Non-IP: Source MAC address
IPv4: Source MAC address
IPv6: Source MAC address
Load-Balancing Operational Parameters:
Hash algorithm: CRC
Asymmetric hashing: disabledRefer to the exhibit. A network engineer notices that on a four-link EtherChannel bundle between two switches, all traffic from a particular VLAN is being forwarded over only one physical link, while the other three links remain idle. The engineer suspects a load-balancing issue and issues the show etherchannel load-balance command, the output of which is shown. What is the most likely cause of the uneven traffic distribution?
⚠ Common exam trap
Cisco often tests the misconception that load-balancing issues are caused by misconfiguration or STP, when the real problem is the hash algorithm's behavior with a single dominant source MAC address.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The switch is using source‑MAC‑address load balancing, and multiple end hosts are appearing with the same source MAC address.
The output of 'show etherchannel load-balance' indicates the switch is using source-MAC-address load balancing. With this method, all frames from a given source MAC address are hashed to the same physical link. If multiple end hosts in the VLAN are actually behind a single upstream router or firewall that uses the same source MAC address for all traffic (e.g., due to proxy ARP or NAT), then all traffic from that VLAN will be pinned to one link, leaving the other three idle.
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 switch is using source‑MAC‑address load balancing, and multiple end hosts are appearing with the same source MAC address.
Why this is correct
The show etherchannel load-balance output confirms the global load‑balancing method is src‑mac. With this method, frames with an identical source MAC always hash to the same physical member link, causing all traffic from hosts sharing that MAC to use only one link.
- ✗
The EtherChannel is misconfigured with an LACP active/passive mode mismatch, forcing only one link to bundle.
Why it's wrong here
An LACP mode mismatch prevents the EtherChannel from coming up at all; it would not show a formed bundle with only one active link. The exhibit does not display LACP state, only the load‑balancing algorithm.
- ✗
VLAN pruning on the trunk has removed the VLAN from three of the four member interfaces.
Why it's wrong here
VLAN pruning controls which VLAN traffic is allowed on a trunk. If the VLAN were removed from three members, those members would not carry any traffic for that VLAN, but they would still carry other VLANs and would not be idle for all traffic. The exhibit does not mention VLAN pruning.
- ✗
Spanning Tree Protocol has blocked three of the four links in the EtherChannel because they form a loop.
Why it's wrong here
STP treats a correctly configured EtherChannel as a single logical interface. Unless there is a misconfiguration (e.g., port‑channel members in different STP states), all members should share the same STP state. The exhibit shows no STP information, and a blocked state would not be caused by the load‑balancing setting.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓The switch is using source‑MAC‑address load balancing, and multiple end hosts are appearing with the same source MAC address.Correct answer▾
Why this is correct
The show etherchannel load-balance output confirms the global load‑balancing method is src‑mac. With this method, frames with an identical source MAC always hash to the same physical member link, causing all traffic from hosts sharing that MAC to use only one link.
✗The EtherChannel is misconfigured with an LACP active/passive mode mismatch, forcing only one link to bundle.Wrong answer — click to see why▾
Why this is wrong here
Candidates may think that an LACP problem explains a single active link, but a mismatch would cause the entire EtherChannel to fail, not selectively use one member.
✗VLAN pruning on the trunk has removed the VLAN from three of the four member interfaces.Wrong answer — click to see why▾
Why this is wrong here
Candidates might mistake an idle member for a pruned VLAN, but pruning would not affect all traffic, only the specific VLAN, and it is not related to the load‑balance method shown.
✗Spanning Tree Protocol has blocked three of the four links in the EtherChannel because they form a loop.Wrong answer — click to see why▾
Why this is wrong here
Candidates may associate an idle link with STP blocking, but an EtherChannel bundle presents one logical link to STP. A blocking state on some members only would indicate a serious configuration error, not the load‑balance method shown.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Visual reference
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
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Last reviewed: Jul 4, 2026
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