With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
appnPortMaxRcvBtuSize
appn Port Max Receive Btu Size
1.3.6.1.2.1.34.4.1.1.4.1.1.10
Maximum Basic Transmission Unit (BTU) size that a link station on this port can receive. This object corresponds to bytes 21-22 of XID3.
Back to APPN-MIB MIB page.
IPHost Network monitor allows you to monitor appnPortMaxRcvBtuSize on Cisco device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Cisco wireless switches right now.