With IPHost Network Monitor you can run simple snmp requests against a IBM device in your network.
ipv6AddrPfxLength
ipv6 Address Pfx Length
1.3.6.1.2.1.55.1.8.1.2
The length of the prefix (in bits) associated with the IPv6 address of this entry.
Back to ibm-ipv6 MIB page.
IPHost Network monitor allows you to monitor ipv6AddrPfxLength 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.