Class B Network

A class B network is a type of network in the now-defunct classful networking architecture. The classful networking architecture defined a range of network classes: A, B, C, D and E. Class B networks have IP addresses between 128.0.0.0 and 191.255.255.255. The Classful networking system has been superseded by CIDR (Classless Inter-Domain Routing) since 1993.

Technipages Explains Class B Network

Classes A, B, and C provided unicast addresses for networks of three different network sizes. Class D was for multicast networking and the class E address range was reserved for future or experimental purposes. IP addresses have 32 binary bits of information split into four-octet bytes. Class B networks use the first two octets to define the network number and the second octets are used to describe the host addresses available in that network.

Class B networks are defined as being between 128.0.0.0 and 191.255.255.255. In modern CIDR notation, a class B network would have the subnet mask /16, there would be a total of 16,384 possible networks and 65,536 possible individual host IP addresses per network. Before the introduction of the classful networking system, IP addresses were handed out to companies in blocks that would become Class A or /8. Given the design of IPv4 addresses, there can only be 256 class A networks and so the classful system was seen as a way to conserve the available IP address space by handing out smaller networks.

Common Uses of Class B Network

• A Class B network was a network in which all addresses had the two most-significant bits set to 1 and 0 respectively.
• The pool of unassigned Class B addresses was rapidly depleted.
• Sixteen contiguous class B networks are reserved for private network addresses.

Common Misuses of Class B Network

• Class B networks are the second-best, they don’t have the same reliability as Class A networks.