Deep decomposition of subnets: compulsory course for network architects

In computer networks, subnetting is the process of dividing a large network logic into several smaller networks. It's not just about managing it effectively. IP address space, especially for enhancing network security and performance.

Why do you want to divide the subnet?

Reduction of broadcasting storms: In a large flat network, the radio packs are sent to all equipment, causing network congestion. Subnet division can limit broadcasting to a smaller range.
Enhancing security: Through the subnet, you can use routers or firewalls to establish logical isolation between different sectors (e.g., finance and outsourcing).
Optimization of address utilization: CIDR (unclassified inter-domain route) allows the distribution of address blocks according to actual needs, avoiding traditional A/B/C The classification of types of addresses is a waste of time.

How do you calculate the subnet? Explanation of core terms

Network Address: Subnet's initial address, with all the hosts 0. It is the symbol of the subnet itself and cannot be assigned to the equipment.

Broadcast address (Broadcast Address): The end address of the subnet, with the host area at 1. The package sent to this address is distributed to all hosts in the subnet.

Subnet Mask: Distinguishing between which of the IP addresses represents the network and which represent the host. For example: 255.255.255.0 Corresponds to CIDR /24 。

Available host range: The IP address that can really be allocated to computers, servers or routers after the network and broadcast addresses have been excluded.

Contexts for addressing specific issues

Scenario one: a network of planning offices. If you're in charge of an office with 50 computers, use /24 The use of the Internet is a waste of a lot of addresses. You can find it in the calculator. /26 (62 available IPs) More precise and residual.

Scene 2: Check IP conflicts. When two device tips In times of conflict, first of all, check their subnet mask for consistency. If inconsistent, they may consider themselves in different segments, which makes it impossible for the gateway to correctly transmit data.

Scenario three: Configure cloud server security. When you configure firewalls for Aliyun or AWS, you usually need to enter a CIDR format. This tool will help you quickly move an IP Change range to standard 10.0.0.0/16 This format.