After interviewing a customer to understand wireless client requirements, you determine that
802.11b must be enabled to support legacy clients within a mixed-mode environment. Which
recommendation will have the greatest impact on mitigating the effects of 802.11b clients on the
rest of the network?
A.
Restrict OFDM modulation from being used.
B.
Make 11 Mb/s the lowest mandatory rate.
C.
Enable a separate SSID for 802.11b clients.
D.
Enable a short preamble.
Make 11 Mb/s the lowest mandatory rate.
You must carefully plan the process to disable or enable data rates. If your coverage is sufficient, it is often a good idea to slowly disable lower data rates one by one. Management frames like ACK or beacons will be sent at the lowest mandatory rate (typically 1Mbps) which slows down the whole throughput.
You might make a conscious decision to not disable all rates below 11Mbps (included) in order to stop the support of 802.11b-only clients.
http://www.cisco.com/c/en/us/support/docs/wireless-mobility/wireless-lan-wlan/82463-wlc-config-best-practice.html#anc5