ConceptIn IPv4 classful addressing scheme, address is divided in 5 typesTypes: Class A, Class B, Class C, Class D and Class E)IPV4 size consists of 32 bits.Classful addressing schemeClassLeading bits (Reserved)Network ID (bits)Number of NetworksHost ID (bits)Start AddressEnd AddressClass A0827240.0.0.0127.255.255.255Class B101621416128.0.0.0191.255.255.255Class C110242218192.0.0.0223.255.255.255Class D1110Not DefinedNot DefinedNot Defined224.0.0.0239.255.255.255Class E1111Not DefinedNot DefinedNot Defined240.0.0.0255.255.255.255 Range of Class B: 128.0.0.0 to 191.255.255.255Range of 1st octet is 128 to 191Therefore, the range of the first (leftmost) octet values of the IPv4 Class “ B address is 128 to 191.