tRPOperPrefixListBeginLength 1.3.6.1.4.1.6527.3.1.2.17.1.1.8.1.8

When tRPOperPrefixListType set to range(4), the mask length to use as the lower limit for the mask range. Must be larger than tRPOperPrefixListMask and less than tRPOperPrefixListThroughLength.