Knowledge Building an Office Network: Necessary Equipment, Steps, and Key Considerations

An office network is a system that connects multiple devices in a company—such as PCs, printers, and servers—so they can communicate with one another, share data, and access the internet. Generally, it involves two elements: an internal network, called a LAN (Local Area Network), and an external network connection, called a WAN (Wide Area Network).

A LAN is a network that connects devices within a limited area, such as the same building or the same floor. The reason you can send print jobs from a PC to a printer or access a file server within the office is because of the LAN. LANs can be wired, which use physical cables, or wireless, which connect via radio waves.

A WAN refers to a wide-area network that connects multiple LANs across geographically separated sites—for example, a Tokyo headquarters and an Osaka branch. This enables data exchange with remote offices. The internet is one type of WAN, but corporate WANs typically use secure connection services such as carrier-provided VPNs or dedicated lines.

Both wired and wireless LANs have advantages and disadvantages in terms of speed, stability, and flexibility, so it’s important to choose based on the office environment and working style.

In many offices, a hybrid setup is used: wired LAN for servers and mission-critical PCs that require stability, and Wi-Fi in meeting rooms or hot-desk areas.

Building an office network requires several specialized devices. Below is an explanation of each device’s role.

The foundation is a fast, stable line to connect to the external internet. In many countries fiber-optic internet is commonly available. Depending on the area you may need to choose from available infrastructure such as cable lines or dedicated lines.

A router relays data between the internal network (LAN) and the external internet (WAN), directing traffic to the correct destination—like a command center for the network. Many routers include basic security features such as a firewall to block unauthorized access. However, for more advanced security, dedicated firewalls or UTM devices are recommended.

As the number of office PCs and printers increases, the router’s LAN ports alone may not be enough. A switching hub, or switch, efficiently connects multiple devices to the network and forwards data to the correct destination, enabling more devices to connect reliably.

A wireless LAN access point connects devices such as smartphones and laptops to the LAN wirelessly by transmitting and relaying radio signals. Wi-Fi routers that combine router and access point functions also include this capability, but for large offices or multi-floor coverage, installing multiple dedicated access points expands coverage and ensures stable communication.

For wired networks, LAN cables connect devices such as routers, switches, and PCs. LAN cables have category standards based on speed and noise resistance. To maximize network performance, it’s important to choose cables that match the specifications of the equipment being used.

A server is a computer that provides functions and services such as file sharing, email, and business applications. Options include on-premises (installed physically in the office) and cloud-based (using cloud services). Choose based on purpose, budget, and security requirements.

Here is the basic flow for building an office network, explained in four steps.

First, understand the current network environment and identify issues—for example, communication slows down at certain times, there are areas where Wi-Fi is hard to connect to, or there are concerns about security. Then clarify the requirements for the new network, considering the number of PCs to connect, business systems to use, and future headcount growth.

Once requirements are clear, design a network diagram (topology). Decide where to place routers, switches, and access points; define IP address assignment rules; and determine the scope of security measures. Considering future scalability and ease of operations at this stage is extremely important for long-term stability.

Based on the design, select the necessary network equipment and purchase or lease it. After the equipment is ready, install routers and switches and perform LAN cabling work according to the design. In particular, ensure neat cable routing and, if possible, use underfloor or ceiling spaces to improve appearance and maintenance.

After installation and cabling are complete, perform initial configuration of each device: router internet connection settings, security settings (firewall, encryption method), and IP settings for each PC. After all settings are complete, carefully test connectivity, speed, and whether access controls work as designed. If there are no issues, begin operations.

To build a comfortable and secure office network and operate it stably over the long term, keep these important points in mind.

It is essential to account for future expansion and headcount growth. Choose switches with extra ports, set a wider private IP address range, and build a flexible configuration that can adapt to growth.

Traffic volume is the amount of data flowing on the network. Required traffic varies greatly depending on work activities such as web conferencing or large file transfers. If usage exceeds the processing capacity of equipment or the line, speed will drop. Understand actual usage and select equipment and lines that can handle peak traffic.

Office networks face constant cyber threats. Since router firewalls provide only basic protection, corporate networks are generally recommended to implement dedicated security devices such as firewalls and UTM (Unified Threat Management) to prevent unauthorized access, malware infections, and data leakage. Encryption and antivirus software are also essential. In addition, regularly providing employee security training is important to raise awareness across the organization.

An IP address is used for identifying devices on a network. If IP addresses overlap within the same network, communication issues can occur. Clearly define which device gets which address, centralize management using a registry, and operate in a planned manner to avoid duplication or shortages.

Networks are not “done” once built—continuous operation and maintenance are essential. Prepare for fast incident response, daily monitoring, and regular reviews of security settings. Either assign an in-house specialist or contract with an external provider so you can respond quickly when trouble occurs.

Optimal network configurations vary depending on office size. Here are two representative examples.

For small offices with a few to several dozen employees, a relatively simple configuration is possible. Bring in an internet line and install one router. Add ports with a switching hub based on the number of PCs and printers and connect devices via wired LAN. If Wi-Fi is needed, use a router with Wi-Fi capability or install a dedicated access point separately.

For offices spanning multiple floors or companies with multiple locations, a more complex configuration is required. Build a hierarchical network using a high-performance core router and switches on each floor. To connect multiple sites, build a secure WAN using carrier-provided VPNs, dedicated lines, SD-WAN, etc. Because management becomes more difficult, design and operation by a knowledgeable specialist or an external vendor is recommended.

Related article: Overview of business reviews and other measures for creating a smart office

Building an office network requires specialized knowledge. If handling it in-house is difficult, consider hiring a specialist vendor.

A specialist can propose an optimal network design tailored to your situation and needs. Many vendors also provide one-stop support—from equipment selection and cabling work to configuration and post-launch maintenance—significantly reducing the burden on your own staff. Another major benefit is receiving expert recommendations based on the latest security threats.

When selecting a vendor, first confirm whether they have extensive experience building networks for offices of a similar size. Also check whether they listen carefully to your needs and explain technical details clearly. Review post-build support and pricing in advance and obtain quotes from multiple vendors for comparison.

Building an office network is an important foundation supporting operational efficiency and security. To succeed, it’s essential to understand basic mechanisms such as LAN and WAN, choose equipment suited to your company’s size and workstyle, and create a careful design that accounts for future scalability and security. Use the steps and points explained in this article to build a comfortable and secure network environment. If you’re concerned about building it in-house, leveraging a specialist vendor is also a valid option.

KDDI provides total IT infrastructure solutions optimized for your office, including LAN cabling, Wi-Fi deployment, and security measures. 

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