CCNA Switching and Network Access Practice Question
A switchport on one side of a link is configured as a trunk, but the peer side is configured as an access port. What is the most likely result?
⚠ Common exam trap
Don't assume mismatches always result in physical link failure; focus on logical traffic handling issues.
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 link roles are mismatched, so VLAN traffic will not be handled as intended.
The most likely result is a logical mismatch that prevents VLAN traffic from crossing the link as intended. In practical terms, one side is trying to carry multiple VLANs with tagging behavior, while the other side is treating the connection as a normal one-VLAN endpoint port. That disagreement usually leads to unexpected or failed traffic behavior. This is a classic switching mismatch scenario. The link may still be physically up, but the two sides do not agree on how the traffic should be handled.
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 link roles are mismatched, so VLAN traffic will not be handled as intended.
Why this is correct
This is correct because a switchport configured as trunk on one side and access on the other creates a Layer 2 mismatch: the trunk side expects IEEE 802.1Q-tagged frames for multiple VLANs, while the access side expects untagged frames on a single VLAN. As a result, VLAN traffic is not forwarded consistently—frames tagged by the trunk are often dropped by the access port, and untagged frames from the access side may be mishandled. The link may still go up (depending on DTP settings), but the intended VLAN segmentation and inter-switch trunking behavior are broken.
- ✗
The access side automatically becomes a routed port.
Why it's wrong here
This is wrong because a trunk/access mismatch is purely a Layer 2 interface-mode configuration issue; it does not alter the port's Layer 3 capability. An access port remains a Layer 2 switching port, and it cannot spontaneously become a routed port (an L3 interface with an IP address) due to a mismatch on the far end. Converting a port to a routed port requires an explicit 'no switchport' command, which has nothing to do with the neighboring switch's trunk configuration.
When this WOULD be correct
In a different question scenario where a switchport is explicitly configured to operate as a routed port and is connected to another switchport configured as an access port, the access port could be described as behaving like a routed port due to its Layer 3 capabilities being utilized.
- ✗
Both switches automatically synchronize their switchport settings.
Why it's wrong here
This is wrong because switchport settings—such as trunk, access, or dynamic modes—are locally significant and are never automatically synchronized or copied between switches. While protocols like DTP can negotiate a common trunking state (if both sides support and allow it), the actual configured mode on one switch does not propagate to the other, and a mismatch remains a persistent configuration error. In this scenario, the access side does not 'learn' to become a trunk; it simply keeps its locally configured access mode.
When this WOULD be correct
In a different question scenario where both switches are designed to support automatic configuration protocols like Cisco's Dynamic Trunking Protocol (DTP), a question could ask what happens when one switch is set to negotiate trunking while the other is set to access mode. In this case, synchronization could occur if both sides were configured to use DTP.
- ✗
The mismatch forces OSPF to change router IDs.
Why it's wrong here
This is wrong because OSPF router IDs are determined by configured router-id values, the highest loopback IP, or the highest active interface IP—completely independent of Layer 2 switchport modes. A trunk/access mismatch affects only VLAN tagging and frame forwarding on the link, not the router ID selection process. Since the mismatch occurs at Layer 2, it has no bearing on OSPF's router ID, which is a Layer 3 routing protocol concept.
When this WOULD be correct
If the question were about OSPF behavior in a scenario where a router's interfaces are misconfigured, such as having a mismatched network type or area configuration, then a change in router IDs could occur due to OSPF recalculating its topology. In that case, the option would be correct.
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 link roles are mismatched, so VLAN traffic will not be handled as intended.Correct answer▾
Why this is correct
This is correct because a switchport configured as trunk on one side and access on the other creates a Layer 2 mismatch: the trunk side expects IEEE 802.1Q-tagged frames for multiple VLANs, while the access side expects untagged frames on a single VLAN. As a result, VLAN traffic is not forwarded consistently—frames tagged by the trunk are often dropped by the access port, and untagged frames from the access side may be mishandled. The link may still go up (depending on DTP settings), but the intended VLAN segmentation and inter-switch trunking behavior are broken.
✗The access side automatically becomes a routed port.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because an access port does not automatically convert to a routed port when connected to a trunk port; it remains an access port and will not participate in Layer 3 routing.
★ When this WOULD be the correct answer
In a different question scenario where a switchport is explicitly configured to operate as a routed port and is connected to another switchport configured as an access port, the access port could be described as behaving like a routed port due to its Layer 3 capabilities being utilized.
Why candidates choose this
Candidates may find this option tempting because they might confuse the concepts of access ports and routed ports, leading them to believe that any misconfiguration would trigger an automatic change in port type.
✗Both switches automatically synchronize their switchport settings.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because switchport settings do not automatically synchronize between devices; each port retains its configuration independently, leading to a mismatch in link roles.
★ When this WOULD be the correct answer
In a different question scenario where both switches are designed to support automatic configuration protocols like Cisco's Dynamic Trunking Protocol (DTP), a question could ask what happens when one switch is set to negotiate trunking while the other is set to access mode. In this case, synchronization could occur if both sides were configured to use DTP.
Why candidates choose this
Candidates may find this option tempting because they might recall concepts related to automatic negotiation protocols, leading them to assume that switch configurations can synchronize without manual intervention.
✗The mismatch forces OSPF to change router IDs.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because the configuration mismatch between a trunk and an access port does not directly affect OSPF router IDs, which are determined by the OSPF process itself and not by switchport configurations.
★ When this WOULD be the correct answer
If the question were about OSPF behavior in a scenario where a router's interfaces are misconfigured, such as having a mismatched network type or area configuration, then a change in router IDs could occur due to OSPF recalculating its topology. In that case, the option would be correct.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of how OSPF operates and the assumption that any configuration mismatch would lead to OSPF changes, reflecting a common misconception about routing protocols and their dependencies on interface settings.
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
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
Go deeper
Related to this question
Learn chapter
Configuring Switch Ports for Desktops, VoIP Phones, APs, IoT, and Virtualized Hosts
Key term
VLAN
A VLAN (Virtual Local Area Network) is a logical grouping of network devices that behave as if they are on the same physical network segment, regardless of their actual physical location.
Key term
Access port
An access port is a switch port that connects to a single end device, like a computer or printer, and carries traffic for only one VLAN.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.