easyMultiple Choice
CCNP Practice Question: The default STP port cost for a 10 Gigabit…
What is the default STP port cost for a 10 Gigabit Ethernet interface?
⚠ Common exam trap
Cisco often tests the difference between the old 16-bit cost values (e.g., 19 for 100 Mbps, 4 for 1 Gbps) and the new 32-bit cost values (e.g., 2 for 10 Gbps), so candidates mistakenly apply the older cost table to 10 Gigabit Ethernet and choose 4 or 19.
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
✓
2
The default STP port cost for a 10 Gigabit Ethernet interface is 2, as defined by the IEEE 802.1D-2004 standard (which uses a 32-bit path cost formula: 20,000,000 / link speed in Mbps). For 10 Gbps (10,000 Mbps), the calculation is 20,000,000 / 10,000 = 2,000, but the standard caps the cost at a maximum of 200,000 and a minimum of 1, with 10 Gbps assigned a cost of 2. This value is used by Rapid PVST+ and MST in Cisco IOS.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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1
Why it's wrong here
A spanning-tree path cost of 1 is reserved for links operating at 100 Gbps or higher, not for a 10 Gbps Ethernet link. Under the standard IEEE 802.1t cost table, 10 Gbps maps to a cost of 2, so selecting 1 falsely indicates a faster link. This distortion can alter root-port elections and make STP prefer a link that is not actually the best path.
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2
Why this is correct
A cost of 2 is the correct path-cost value for a 10 Gbps link in the IEEE 802.1t short-method table. This value is part of the revised non-linear cost scale, where lower costs represent higher bandwidths, and 10 Gbps specifically corresponds to 2. Using this value ensures accurate Spanning Tree calculation for 10 Gbps interfaces, making it the right choice for the question.
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4
Why it's wrong here
A path-cost value of 4 is the standard STP cost for a 1 Gbps link, not for a 10 Gbps link. If a 10 Gbps port is incorrectly assigned cost 4, Spanning Tree will treat it as if it were only gigabit speed, which can make equal-cost paths across 1 Gbps and 10 Gbps links appear identical. This could lead to suboptimal blocking decisions or unbalanced forwarding, so 4 is wrong for 10 Gbps.
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19
Why it's wrong here
A cost of 19 is the legacy and 802.1t cost value for a 100 Mbps Fast Ethernet link, which is far slower than 10 Gbps. Since STP prefers the lowest cumulative path cost to the root bridge, assigning 19 to a 10 Gbps port would make it appear extremely expensive and likely cause the port to be blocked in favor of other 10 Gbps links with cost 2. Therefore, 19 does not represent the correct cost for 10 Gbps.
Visual reference
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-401 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 350-401 exam.