sleGponOnuHostIPv6PrefixLen

Denotes the length of a generic Internet network address
prefix. A value of n corresponds to an IP address mask
which has n contiguous 1-bits from the most significant
bit (MSB) and all other bits set to 0.
          
An InetAddressPrefixLength value is always interpreted within
the context of an InetAddressType value. Every usage of the
InetAddressPrefixLength textual convention is required to
specify the InetAddressType object which provides the
context.  It is suggested that the InetAddressType object is
logically registered before the object(s) which use the
InetAddressPrefixLength textual convention if they appear in
the same logical row.
          
InetAddressPrefixLength values that are larger than
the maximum length of an IP address for a specific
InetAddressType are treated as the maximum significant
value applicable for the InetAddressType. The maximum
significant value is 32 for the InetAddressType
'ipv4(1)' and 'ipv4z(3)' and 128 for the InetAddressType
'ipv6(2)' and 'ipv6z(4)'. The maximum significant value
for the InetAddressType 'dns(16)' is 0.
          
The value zero is object-specific and must be defined as
part of the description of any object which uses this
syntax. Examples of the usage of zero might include
situations where the Internet network address prefix
is unknown or does not apply.