About Subnetting
A network is comprised of IP (Internet Protocol) addresses. This is also known as the network address. In order to break down to smaller sub-networks, also known as subnets, a process called subnetting is employed. A network may have multiple layers, usually with the subnet as the non-physical ID of each one. The physical layer would be the hosts (for example, computer or server), hubs, switches and routers; each device is assigned, whether manually or dynamically, its own IP address.
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The Facts
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Subnetting is subdivided into two forms of subnet notation: the standard notation and CIDR (Classless Internet Domain Routing) notation. Both of them use network addresses that define the starting point of the network--for example, 192.168.1.0 with the first host IP address possible within the same subnet would be 192.168.1.1.
To create subnetworks, you take bits from the host portion of the IP address and reserve them to define the subnet address. This means there would be fewer bits for hosts, so the more subnets, the fewer bits available for defining hosts.
Identification
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For the subnet address scheme to work, every machine on the network must know which part of host address will be used as a subnet address. This is accomplished by assigning a subnet mask to each machine. There are two parts that comprise each IP address. One is to identify the network ID, and the other to identify the node or host IP. To identify which part belongs to the network address and which part belongs to the node address, you need to determine which class the IP address and subnet mask belong to.
IP Addresses are identified by 5 different classes. To identify where your IP address belongs to, you can examine the first 4 bits of the IP address.
Class A addresses start with 0xxx, or 1 to 126 decimal.
Class B addresses start with 10xx, or 128 to 191 decimal.
Class C addresses start with 110x, or 192 to 223 decimal.
Class D addresses start with 1110, or 224 to 239 decimal.
Class E addresses start with 1111, or 240 to 254 decimal.Default Subnet Mask:
Class A Format Net.Node.Node.Node Default Subnet Mask 255.0.0.0
Class B Format Net.Net.Node.Node Default Subnet Mask 255.255.0.0
Class C Format Net.Net.Net.Node Default Subnet Mask 255.255.255.0 -
Benefits
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There are many reasons to use subnetting:
1) Reduced network traffic. Subnetting, by use of rotuers, would allow for better network traffic flow. Routers allow most traffic to stay within the local network except when packets need to go to other networks, which will then pass through the router. Since routers create broadcast domains, the smaller domains created, the lesser network traffic is in that segment.
2) Optimized network performance. When network traffic is reduced, the performance is optimized.
3) Simplified management. With subnetting, it is easier to isolate the problem once identified since you drill down in smaller sub networks as opposed to one big network.
4) Facilitated spanning of larger geographical distances. Because WAN (Wide Area Network) links are more expensive and slower than the LAN (Local Area Network) links, a single huge network that spans long distances has more problems than that of multiple smaller networks connected to each other. Subnetting allows for a more efficient way of networking and managing networks.
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