cdtIfIpv6NdPrefixLength 1.3.6.1.4.1.9.9.784.1.2.1.1.19

This object specifies the length of the IPv6 prefix specified by the corresponding instance of cdtIpv6NdPrefix. This column is valid only if the 'ipv6NdPrefix' bit of the corresponding instance of cdtIfValid is '1'.