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How to configure multiple networks on one router

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Anyone who spent late nights playing video games in their friend’s dorm remembers the joys of setting up a local-area network (LAN) in the days before Wi-Fi. While setting up multiple LANs made for a fun night of gaming with friends, setting up multiple networks on a single router offers a number of vital benefits to today’s businesses and IT professionals.

But given the headaches of deploying and maintaining just a single network on a router, many network admins – or just those managing networks at home – tend to shy away from configuring multiple LANs on a single router.

Before we dive into how to configure multiple networks on a single router, let’s talk about why it can be beneficial.

Why setup Multiple LANs?
While there are many use cases for creating multiple networks, the key benefits are cost savings, security, and access control to specific areas of your network.

While it’s entirely possible that businesses paid to buy and maintain the devices for each separate network, in a small business, this can be accomplished on a single wireless router if that device supports it. For example, many wireless router vendors support a wizard-based configuration for the regular home or small business user. Usually, this is limited to 2 LANs—one for your private network and one for a guest network, for everyone else.

For a large company that needs to deliver Wi-Fi to the entire business, but segment the finance department’s data from marketing while shielding HR data from malicious outsiders, configuring requires an understanding of how networking hardware creates a network and deliver traffic through it. This wouldn’t be configured on a wireless router but on a dedicated router or multi-layer switch.

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What do I need to understand?
To accomplish this for a business, you should have a good understanding of Internet Protocol (IP) addresses. This lays the foundation for how the Internet and all of our connected devices interact with each other, giving unique numerical identifiers to everything and everyone on the Internet. Within a private home or office network, every router, switch, modem, and other networking hardware has a set IP address. A single IP address divides into two sections: Network ID and Host ID.  The Network ID defines the logical group where devices belong.  The remaining section (Host ID) represents the unique device within that grouping.  To apply multiple networks, we must understand where the network division happens to create multiple smaller networks.

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When we understand how traffic flows through networks, we can dive into the two main ways to set up multiple LANs on a single router: subnets and virtual local area networks (VLANs).

Subnets
Subnets are the logical groups of addresses that we use to separate networks. A single network can also be subnetted. Subnetting takes a single network and subdivides it into smaller networks. Why would I do it? Let’s say your working with an existing network address block assigned to you. You can use subnetting to re allocate it to be more useful to you by creating smaller networks called “subnets.”

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For instance, let’s consider a typical corporate office. You may have been assigned a single address block—1 network with a certain number of hosts per network. But you have Finance, Marketing, and HR departments which have specific needs for security and bandwidth. The router is the networking machine that regulates traffic and sends packets between an internal network and the outside world. It will be configured with an interface for each department – finance, marketing, and HR would each have a subnet. These interfaces will have an IP address on them that will become the default gateway address for each subnet, and the router will route traffic between the subnets and out to the Internet.

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Subnetting networks is a powerful way enterprise IT teams regulate and manage the security needs of each department they serve, but it’s not always the best fit for every network. Virtual local area networks perform similar functions by leveraging hardware resources to segment a network, instead of setting IP masks to segment traffic.

Virtual Local Area Networks (VLANs)
A physical switch is logically equal to a single LAN.  VLANs allows us to take a single physical switch and logically group ports into multiple smaller switches.  Each smaller group would be a VLAN.  This is no the only configuration though.  A single VLAN can also span multiple switches to regroup ports from multiple switches to work as a single switch.

For at-home enthusiasts, VLANs cordon off traffic to offer a strong layer of security to protect against intruders attempting to sniff packets on your network. For enterprise network engineers, however, VLANs deliver invaluable improvements in efficiency. IT engineers often have to compartmentalize specific services to different areas of the network; rather than building independent infrastructure for each service, VLANs give the flexibility to construct a virtual network as needed for a vital or load-intensive service without the need for additional hardware.

For enterprise networks, subnets and VLANs are often used in conjunction to work on the network’s different broadcast layers.

VLANs also mean your network isn’t tied to specific hardware. So, if your finance department moves to another office, transitioning their network can be done completely through software instead of migrating an entire network infrastructure.

How to Configure Multiple Networks
Now that we understand the common ways of deploying multiple networks, we can think of the best way to set up multiple LANs by creating a subnet or VLAN on a private network. While this does not typically require any custom software beyond a browser, you’ll often want a physical, wired connection to your router hardware and an understanding of how to manipulate your server software. Let’s walk through a few important terms and steps.  For the home user, this will be limited but useful.

Default Gateway Addresses
The default gateway address is an important element in setting your network appropriately. Like it sounds, a default gateway is the intermediary between your local network and the Internet, but also allows the devices on the network to communicate with each other. At home, this is typically your router which accepts an Internet signal from your modem and shares it to the network. You’ll need to know your default gateway IP address to set up subnet masks within your network to segment traffic. In Windows, you can open the Command Prompt and type: ipconfig | findstr /i “Gateway” to learn the default gateway IP.

Logging Into Your Wireless Router
Knowing the default gateway address will let you log into your router and begin to manage subnets or VLANs. Most consumer-based routers have default IP addresses that make it easy to log in. Cisco routers, for instance, typically are 192.168.1.1, with passwords of admin or cisco. You can always do a search with your favorite browser for the default password for your brand and model. If you don’t already have a LAN up and running, you’ll probably need an Ethernet cable to connect your computer to the router.

Setting a Subnet or VLAN
For the home, just walk through the wizard provided to set up an additional VLAN if your router supports it.  Just make sure you know your subnet and have chosen the default gateway address to configure.
In a business or enterprise, creating a subnet or virtual network does require knowledge of how the router assigns IP addresses or allocates network resources, some devices will have a web interface but will be more detailed and require more setup. When creating a subnet, you’ll be creating IP addresses that live under the default gateway IP address. For instance, thinking about the Finance department in our earlier example: if the default switch IP address is 176.16.0.0, Finance would be 176.16.10.0/24 while Marketing would be 176.16.20.0/24. Each lives under the gateway IP, but the router knows to send Marketing traffic and Finance appropriately.

As you can imagine, creating a subnet often requires a dedicated IT professional. Selecting the right subnet mask requires calculating how many binary bits your subnet will require to support the devices you need, and then they must be applied within the network infrastructure.

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For most people, especially at home, a VLAN will solve most of their issues – like creating a Guest network within your Wi-Fi network or setting up multiple LANs to support things like streaming or multiple game systems on the same network.

To create a VLAN, which often operate within a subnet, you’ll typically find the LAN >> VLAN configuration options within your router. You’ll select the LAN subnet, select which ports on your router should be dedicated to the VLAN, enable VLAN tags and set IDs for each. Once your VLAN is up and running within a subnet, you can set security and access restrictions for the new virtual network running on your single router or network devices. But remember, not every wireless router will support it.

Getting Started
Most networking functions require a deep understanding of networking technology, and it can be difficult to know where to get started. While subnetting provides a scalable, secure method of expanding your networks, it can be difficult for IT enthusiasts to get started. While VLANs are more accessible, they don’t solve the needs of every business or private network.

When you’re ready to learn more and expand your IT networking abilities, ITProTV offers a number of online IT training courses for IT management and technical networking abilities to support everyone from IT enthusiasts to professionals.