Which UNII-2 Channels Must Be Designed for IW3700 WGBs?
A customer has multiple WGBs located around a warehouse to support mobile and stationary industrial machines. The wireless network consists of these components: • two Cisco 5520 WLCs in a high availability cluster • 100 Cisco 2800 APs in local mode • 25 Cisco IW3700 Series APs in WGB mode • WLANs that are all 802.11a only • UNII 1, UNII 2, and UNII 2E channels in use The customer wants to use only UNII 2 channels within the mobile machine area of the warehouse and must reduce the channel scan time on the WGBs. Which channels must be incorporated in the design for the WGBs?
Community Votes
100% of anonymous learners picked answer B. Votes are pick records left by other test-takers — they are not the verified answer.
Community Insight
It tests the 5 GHz UNII band-to-channel mapping in a WGB design context; the trap is drifting to UNII-1 (36–48) because it avoids DFS, even though the customer explicitly scoped the machine area to UNII-2 only.
A warehouse using IW3700 Series APs in workgroup bridge mode must confine the mobile machine area to UNII-2 channels while shortening the WGB channel scan time. This page establishes that the four UNII-2 (UNII-2A) channels 52, 56, 60 and 64 — option B — are the ones that belong in the WGB channel list.
Picking A (36, 40, 44, 48) because UNII-1 is non-DFS and therefore looks like the fastest way to reduce scan time, which ignores the stated requirement that only UNII-2 channels be used in the mobile machine area.
Community Discussion (3 comments)
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Expert Analysis
Why the Answer Is Correct
In the 5 GHz spectrum, UNII-2 (5250–5350 MHz) is exactly the channel set 52, 56, 60 and 64, which is what option B lists. The customer's requirement is twofold: the mobile machine area must operate on UNII-2 only, and the WGB scan time must be reduced, so the IW3700 workgroup bridges must carry a trimmed channel list containing only those four UNII-2 channels rather than scanning the full 5 GHz range. Because the WLANs are 802.11a-only, the IW3700 WGBs search for a parent AP in 5 GHz, and every channel added to the scan list costs off-channel dwell time, so narrowing the list to the four UNII-2 channels directly cuts the scan cycle. The 5520 high-availability cluster and the 100 local-mode 2800 APs define the infrastructure but do not change which channel set the bridge must scan. Choosing B satisfies both the band restriction and the scan-time objective simultaneously.Why the Other Options Are Wrong
Option A (36, 40, 44, 48) is UNII-1 (5150–5250 MHz) — the low band originally intended for indoor use and free of DFS — so it is the most seductive distractor, but it is not UNII-2 and therefore violates the design constraint for the machine area. Option C (100, 104, 108, 112) is UNII-2 Extended (UNII-2C, 5470–5725 MHz), a different band that also carries DFS obligations; the customer's "UNII 2" does not include it. Option D (149, 153, 157, 161) is UNII-3 (5725–5850 MHz), a high-power band that is not UNII-2 at all. All three distractors are legitimate 5 GHz bands, which is exactly why the band-to-channel mapping must be memorized rather than guessed.Community Comment Notes
Farhad123 posted a helpful breakdown table that maps each option to its UNII band and flags only option B as UNII-2. AlmightKas reasoned toward A on the grounds that staying below DFS minimizes scan disruption, noting that "UNII 2 and UNII 2e are both subjected to DFS scans" — a fair operational point, but the customer's requirement pins the machine area to UNII-2 regardless of DFS. Jonycici kept it simple, confirming "B. 52, 56, 60, 64 UNII-2 channels", which matches the unanimous vote record for B.Exam Requirements Mapping
This item sits under wireless network type design and radio management: the WGB deployment pattern (industrial machines in a warehouse) plus the channel plan are the two design levers being tested, not controller HA or AP HA.Official Reference
Exam Strategy
Memorize the 5 GHz band map cold: UNII-1 = 36–48, UNII-2/2A = 52–64, UNII-2 Extended/2C = 100–140, UNII-3 = 149–165. Then read the requirement sentence for the word "UNII" plus a number, because every distractor here is a real band that only fails on that band label.
Frequently Asked Questions
Why do only four UNII-2 channels reduce the IW3700 WGB scan time?
A WGB cycles through every channel in its scan list looking for a parent AP, so trimming the list to 52, 56, 60 and 64 keeps the bridge on-channel and off-scan less often.
Why is option C (100–112) wrong if it is also called UNII-2?
Those channels are UNII-2 Extended (UNII-2C, 5470–5725 MHz), a separate band from the UNII-2/UNII-2A channels 52–64 the customer asked for.