etsysDot11ExtMulticastTxRate 1.3.6.1.4.1.5624.1.2.9.1.2.1.1.7

This value specifies the Multicast data transmission rate of the AP. It is implemented when cards that operate faster than the 2Mbit 802.11 standard are inserted. This object must be saved across a system reset and/or a power cycle.