Complex sentence: A prefix length can range from 0 to 128, due to the larger number of bits in the address, however, by convention a subnet on broadcast MAC layer networks always has 64-bit host identifiers.
Split into simpler sentences: A prefix length can range from 0 to 128, due to the larger number of bits in the address. However, by convention a subnet on broadcast MAC layer networks always has 64-bit host identifiers.