Channel Bonding and Mandatory 24 Mbps Data Rates for High Density?
A school deploys a Cisco wireless infrastructure in its classrooms to support a high density of mobile devices. The network administrator wants to bond channels in groups of two and only allow APs to send 802.11 management frames at 24 MB. What should be included in the design to accomplish this objective?
Community Votes
100% of anonymous learners picked answer C. Votes are pick records left by other test-takers — they are not the verified answer.
Community Insight
It tests the difference between a Mandatory (basic) data rate — used for beacons, probes and other management frames — and a Supported rate, plus which PHY actually supports 40 MHz bonding.
In a high-density school deployment, bonding channels in pairs requires a 40 MHz channel on the 802.11a (5 GHz) PHY, and forcing AP management frames to 24 Mbps requires that rate to be Mandatory, not Supported. This page confirms option C as the design that satisfies both requirements.
Selecting Supported for 24 Mbps is the most common error: Supported rates only advertise what clients may use for data, while management frames are always transmitted at the mandatory/basic rate set.
Community Discussion (3 comments)
Comments & Corrections
No comments yet — spotted an error or have a note? Share it below.
Expert Analysis
Why the Answer Is Correct
Bonding channels in groups of two means using one 40 MHz channel instead of two separate 20 MHz channels, which is a capability of the 5 GHz 802.11a OFDM PHY used in this design. On a Cisco wireless controller, the Mandatory (basic) rate set determines the rates used for beacons, probes and all other 802.11 management and control frames, so forcing management frames to 24 Mbps requires marking 24 Mbps as Mandatory. Option C combines exactly these two elements — 802.11a at 40 MHz and 24 Mbps Mandatory — and satisfies both halves of the administrator's objective. It also matches high-density doctrine: raising the basic rate to 24 Mbps reduces airtime consumed by management traffic in crowded classrooms. Because 24 Mbps is one of the standard basic OFDM rates in 802.11a, it can legitimately be set as mandatory.Why the Other Options Are Wrong
Options A and D specify 802.11b, which is the 2.4 GHz DSSS PHY and cannot support 40 MHz channel bonding or a 24 Mbps rate at all, since 802.11b tops out at 11 Mbps. Option B correctly names 802.11a and 40 MHz but marks 24 Mbps as Supported; Supported rates are merely advertised client data capabilities and do not govern the rate at which the AP transmits management frames, so the requirement would not be met. Option D compounds both errors by pairing the wrong PHY with the wrong rate designation.Community Comment Notes
One voter summarized the standard rate behavior, explaining that "The mandatory data rates for 802.11a are 6, 12, and 24 Mbps" while the supported set spans 6 through 54 Mbps, which is why the requirement points to Mandatory. As SrStew noted about the 802.11b options, "supported is wrong, 5ghz better option," correctly steering the design toward the 5 GHz band. Jonycici simply stated "C is correct." All 100 recorded votes selected C, consistent with the mandatory-versus-supported and PHY analysis above.Exam Strategy
On 300-425, translate the wording first: "bond channels in groups of two" means 40 MHz, and "only allow the AP to send management frames at 24 Mbps" means a Mandatory/basic rate. Eliminate any option using 802.11b for high throughput, since 2.4 GHz DSSS cannot do 40 MHz or 24 Mbps.
Frequently Asked Questions
Why must 24 Mbps be Mandatory instead of Supported?
Beacons, probes and other management frames are transmitted at the lowest mandatory/basic rate, so 24 Mbps must be Mandatory; Supported rates only advertise client data capabilities.
Why is 802.11b with 40 MHz wrong here?
802.11b is the 2.4 GHz DSSS PHY with a maximum 11 Mbps rate, so it supports neither 40 MHz channel bonding nor a 24 Mbps rate.