With IPHost Network Monitor you can run simple snmp requests against a IBM device in your network.
ipv6IfStatsInDiscards
ipv6 If Stats In Discards
1.3.6.1.2.1.55.1.6.1.8
The number of input IPv6 datagrams for which no problems were encountered to prevent their continued processing, but which were discarded (e.g., for lack of buffer space). Note that this counter does not include any datagrams discarded while awaiting re-assembly.
Back to ibm-ipv6 MIB page.
IPHost Network monitor allows you to monitor ipv6IfStatsInDiscards on IBM device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring IBM switches right now.