Voice and Location WLAN Design: Overlap and AP Placement?
Short answer
BC Place APs in floor corners for triangulation and use 15% cell overlap to support both voice roaming and location services.
Question
Key Takeaways
Tests whether you know the overlap and AP placement requirements for voice and location services; the trap is choosing an excessive 25% overlap or enabling every channel in 2.4 GHz.
This Cisco 300-425 design question asks which two features let a WLAN handle voice traffic and location-based services simultaneously. The correct design pairs corner AP placement for location triangulation with 15% cell overlap for voice roaming, as confirmed by the answer key and community consensus.
Common mistake: Choosing E (25% cell overlap) because more overlap seems better for location, but Cisco recommends 15-20% for voice and excessive overlap increases co-channel interference and cost.
Expert Analysis
Why the Answer Is Correct
Option B is correct because location-based services rely on trilateration, which requires a client to be heard by at least three APs. Placing APs in the corners and along the perimeter of each floor ensures that clients near walls and edges are still detected by multiple APs, which is a standard Cisco location design guideline. Option C is correct because voice traffic demands 15-20% cell overlap for seamless roaming; 15% falls within that recommended range and also supports location accuracy when combined with proper AP placement. Together, B and C address the two services: location triangulation via AP placement and voice roaming via controlled overlap.Why the Other Options Are Wrong
Option A suggests using every possible 5 GHz channel, but that is not a design requirement for voice or location and can create co-channel interference if not properly planned; it also ignores DFS considerations. Option D is wrong because 2.4 GHz has only three non-overlapping channels, so using every channel would cause severe interference. Option E is wrong because 25% overlap is excessive: Cisco recommends 15-20% for voice, and a larger overlap shrinks cells, increases co-channel interference, and raises deployment cost without improving location accuracy.Community Comment Notes
Jonycici noted that "For Voice you should have between 15% and 20% cell overlap" and that location requires triangulation, which supports B and C. 55f2ace corrected the terminology to "trilateration" while agreeing with the 15-20% voice overlap requirement. Farhad123 observed that choosing C and E together "does not make sense" because they are competing overlap values. Bembs suggested A and B, but that view overlooks the specific overlap needed for voice and treats using every 5 GHz channel as a design feature when it is not.Official Reference
https://www.cisco.com/c/en/us/td/docs/wireless/technology/design/highdensity/highdensity.html
This link opens the official vendor documentation in a new tab.
Exam Strategy
When a question pairs voice with location services, first identify the overlap requirement for voice (15-20%) and the AP placement needed for location trilateration; eliminate any option that exceeds the overlap range or uses all channels in a band. Multi-select questions often include one correct overlap and one correct placement feature.
Frequently Asked Questions
Why is 15% overlap correct instead of 25% for voice and location?
Cisco recommends 15-20% overlap for voice; 15% supports roaming while 25% is excessive and increases interference without improving location accuracy.
Why place APs in corners for location triangulation?
Location trilateration requires at least three APs to hear a client; corner placement ensures edge clients are detected by multiple APs, improving location accuracy.
Community Votes
100% of anonymous learners picked answer BC. Votes are pick records left by other test-takers — they are not the verified answer.
Discussion 5 contributions
Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors, not of islever. The comments shown first are the most substantive of the thread — ranked by depth, community endorsement and relevance; expand the list below to read the rest.
From public community threads 5
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Jonycici 👍 3BC. For Voice you should have between 15% and 20% cell overlap. For Location you should have triangulation.
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91f3856 👍 1A. Use every channel possible in 5 GHz. E. Have a 25% overlap of cell coverage. Using every available channel in the 5 GHz band reduces interference and increases capacity, while a 25% overlap of cell coverage ensures seamless handoffs and accurate location tracking.
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Farhad123 👍 1BC are the right one. we cant have C and E as answers does not make sense .
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55f2ace 👍 1Location uses trilateration Voice and data 15% to 20% cell overlap
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Bembs 👍 1Should be A and B
Reader comments & corrections
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