What is a Subnet?
A subnet, sometimes known as a subnetwork, is a particular area of a larger network. To put it more precisely, subnets are logical partitions of an IP network that are separated into more manageable, smaller sections. By arranging clients logically or according to their location, these subdivisions are frequently used to improve network traffic flow.
A particular range of potential IP addresses is assigned to each subnet. Subnets are used by organizations to divide large networks into more manageable, smaller segments. Partitioning a large network into interconnected smaller networks is one of the main goals of subnet creation, since it aids in reducing traffic congestion. Because fewer superfluous paths must be taken by traffic, this configuration improves network speeds and enables more efficient data transmission.
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Reference: https://en.wikipedia.org/wiki/Subnet#/media/File:Subnetting_Concept-en.svg
The Importance of Subnets
The procedure of addressing a letter is analogous to the idea of subnets. Subnets are used in networking for the same reason that the post office uses a letter’s city, state, and zip code to decide whether it is local and can be handled by that particular sorting facility or if it should be sent to another place for delivery. In the absence of such a system, every post office would have to be aware of the whereabouts of every street across the nation. Instead, each office just needs to use basic routing rules to forward other mail and maintain the addresses that are pertinent to its region when using this addressing system.
Address allocation is made more efficient by subnetting, which divides a network address space. This approach, which is closely related to IP addresses, subnet masks, and Classless Inter-Domain Routing (CIDR) notation, is fully described in the document known as Request for Comments 950.
How do subnets work?
Subnet Communication and Configuration
Direct communication between the devices linked to each subnet is made possible. To enable communication between several subnets, routers are essential. The system administrator chooses a subnet’s size, which is impacted by the network technology being used and the connection needs. A data centre subnet may be built to support many more devices than a point-to-point subnet, which connects two devices.
While adhering to the limitations of the available address space, organizations are in charge of choosing the quantity and dimensions of the subnets they create. Additionally, the details of subnet segmentation inside a company are kept private and limited to that firm. The Network Prefix, sometimes referred to as the Network ID, and the Host ID are the two primary parts of an IP address. Depending on whether the address belongs to Class A, B, or C, the Network Prefix and the Host ID are separated.
Understanding Subnet Mechanisms
To identify subnets, the subnet method makes use of a section of the Host ID field. To specify which portion of the IP is used as the Subnet ID, a subnet mask is used. A binary AND operation is used to apply this mask to the entire network address. Only when both inputs are “true” is the output of this operation regarded as “true”; otherwise, it is “false.” As a result, only when both bits are set to 1 is the Subnet ID obtained. The Host ID is represented by the remaining bits in the address.
In reality, network managers frequently use a subnet’s Subnet ID to refer to it. For instance, one may hear someone state, “Subnet 2 is having problems today,” or “The dot-two subnet is having problems.” Understanding some of the subtleties of IP addresses is crucial to comprehending how subnets might be implemented.
Networks rely on IP addresses to route data between connected devices since it is a connectionless protocol that doesn’t require a central directory or monitoring system. These addresses serve the same purpose as mailing addresses, identifying the postal mail’s source and destination. IPv4 and IPv6 are the two primary IP address variants. A network prefix and a host identification are the two parts of an IP address. Usually, the prefix takes up the majority of the address’s bits.
A 32-bit specification, which is represented by four octets (8-bit units) spanning from 0 to 255, defines IPv4 addresses. Although these addresses are frequently shown in decimal format, subnetting may benefit by changing them to binary.
A bigger network can be split up into smaller sub-networks by creating subnets by stealing bits from the host section of an IP address. To do this, a subnet mask is used. The updated IP address now has a subnet component in addition to the original network and host components.
Classes of Subnetworks
Class A, Class B, Class C, Class D, and Class E are the five different subnet classes. Classes A, B, and C are the most often used across different networks, and each class correlates to a certain set of IP addresses. The number of bits allotted to the network and host portions of their IP addresses determines how unique each subnet class is. The value in the first octet of an address identifies the class, which has a default subnet mask associated with it:
- Class A: First Octet Value 0-126
- Class B: First Octet Value 128-191
- Class C: First Octet Value 192-223
- Class D: First Octet Value 224-239
- Class E: First Octet Value 240-255
It’s crucial to remember that since 127 is reserved for loopback addresses, it is not included in these classes.
What is a Class A IP address?
A Class A IP address allots 24 bits for hosts and 8 bits for the network component. Class A’s default subnet mask is 255.0.0.0, and its range is 0 to 126. When it comes to supporting very big networks, this class is perfect.
Class B IP addresses, on the other hand, are better suited for smaller networks because they save 18 bits for hosts and 14 bits for the network. Class B addresses fall between 128 and 191, and their default subnet mask is 255.255.0.0. Class C IP addresses, which range from 192 to 223, are usually issued to very tiny networks. Class C’s default subnet mask is 255.255.255.0.
It is crucial to realize that, even though it may appear counterintuitive, an IP address’s ability to service subnets within larger networks increases with the number of bits it reserves for the network. There are fewer bits available for hosts to build subnet masks when more bits are allocated to the network since subnetting takes place on the host side of an IP address.
What is the use of Class D and Class E IP addresses?
The primary use of the Class D and Class E IP addresses is for testing. For instance, multicasting applications—which allow a single sender or a group of senders to communicate with multiple recipients simultaneously—are the exclusive use of Class D addresses. Since there are no host bits available in this address space, Class D addresses cannot be sub netted and are not used in typical networking activities like Classes A, B, and C. It’s common knowledge that Class E addresses are reserved for research, development, and future use. But since these addresses haven’t been used in real-world scenarios, many network implementations completely ignore this class. Class E is occasionally thought to be unlawful or ill-defined. The IP address 255.255.255.255 is a noteworthy exception. It functions as a broadcast address, enabling device connections inside a multiple-access communications network.
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