![]() ![]() ![]() This allowed networks to be aggregated, reducing the number of entries in the IP routing tables, whilst also allowing for greater efficiency in IP route processing. Classless networks do not use the subnet masks mandated by the different A, B or C classes, instead, the subnet mask (aka CIDR “bit” notation) is represented - ranging from /8 to /32. Classless Inter-Domain Routing (CIDR)ĬIDR (as per RFC1519) was implemented to allow the routing of both classful and classless networks. Both of which are key to modern day subnetting. The solution to this issue came in the form of - Classless Inter-Domain Routing (CIDR) and Variable Length Subnet Masking (VLSM). With the explosion of the internet and the need to address more and more devices, this issue was compounded and a solution was required. However, this was hugely inefficient, should a company require 2 IP addresses for a point to point link then the smallest classful network that could be assigned was a class C network, which would provide 256 hosts. Each class provided a different subnet mask based upon the IP range. This architecture provided three different network classes - known as class A, B and C. When the IP protocol was first released it was built upon a classful addressing architecture. For example, 255.255.0.0 would result in the first 2 octets (16bits) being the network bits and the remainder being the host bits. ![]() Within a subnet mask, the sequential bits that are on (1) are deemed the network bits and the bits that off (0) are considered the host bits. To determine which parts of an IP address are the network bits, and which are host bits, a subnet mask is used. Host - the host identifier of the device for the network.Network - the network the IP address belongs to.Each octet is 8 bits i.e one byte.Įach address is made up of 2 identifiers (shown below): AddressingĪn IP address (in the case of v4) is built upon 32-bits, expressed in four numbers known as octets. Each host is assigned an IP address which is used to ensure that traffic is sent to the correct destination, synonymous in many ways to a postal address that we place on a letter. IP enables communication between hosts by carrying data within packets. IP is a connectionless protocol that operates at the network layer of the OSI model. Note: The scope of this document covers IPv4 subnetting only. Before we dive into subnetting we will look into the structure of an IP address, along with some of the key IP schemes that assist in modern day IP subnetting. Within this tutorial, we will provide a beginner’s guide to subnetting. ![]()
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