You have a network and you have hosts on the network anything with an IP address is a host. Because I am a simple person, I think of it like this; The network number represents the street I live on, and the host portion is used for the numbers on all the houses on my street. A subnet mask of This means we can have computers on this network, because the fourth octet is not being used by the network portion of the address.
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Internet Protocol IP addresses are the numerical addresses used to identify a particular piece of hardware connected to the Internet. Both IPv4 and IPv6 addresses come from finite pools of numbers. For IPv4, this pool is bits in size and contains 4,,, IPv4 addresses. The IPv6 address space is bits in size, containing ,,,,,,,,,,,, IPv6 addresses. A bit is a digit in the binary numeral system, the basic unit for storing information.
Some IP addresses have been reserved for other uses, such as for use in private networks. This means that the total number of IP addresses available for allocation is less than the total number in the pool. Network prefixes IP addresses can be taken from the IPv4 or the IPv6 pool and are divided into two parts, a network section and a host section.
The network section identifies the particular network and the host section identifies the particular node for example, a certain computer on the Local Area Network LAN. IPv4 The size of the prefix, in bits, is written after the oblique. There is a total of 32 bits in IPv4 address space. From this, the number of bits left for address space can be calculated. This is enough space for host addresses.
These host addresses are the IP addresses that are necessary to connect your machine to the Internet. All IPv6 networks have space for 18,,,,,, IPv6 addresses. To give some perspective, it is worth noting that there are 4,,, IPv4 addresses in total, significantly less than the number of IPv6 addresses.
IPv6 Relative Network Sizes.
CIDR Blocks Table IPv4 and IPv6
Background[ edit ] An IP address is interpreted as composed of two parts: a network-identifying prefix followed by a host identifier within that network. In the previous classful network architecture, IP address allocations were based on the bit boundaries of the four octets of an IP address. An address was considered to be the combination of an 8, 16, or bit network prefix along with a 24, 16, or 8-bit host identifier respectively. Thus, the smallest allocation and routing block contained only addresses—too small for most enterprises, and the next larger block contained addresses—too large to be used efficiently even by large organizations. This led to inefficiencies in address use as well as inefficiencies in routing, because it required a large number of allocated class-C networks with individual route announcements, being geographically dispersed with little opportunity for route aggregation.
CIDR Conversion Table
Understanding IP Addressing and CIDR Charts