VLAN (Virtual Local Area Network) is a way to partition a physical LAN into multiple subnets virtually. You can base these partitions on many criteria, such as building, department, function, or security. They help you create greater flexibility within your network and give you more control over your resources. It achieves this effect by separating or isolating network traffic based on logical boundaries. They can be implemented in numerous ways using either hardware or software options. Enterprise networks, data centers, and other large-scale infrastructures often use them. In essence, VLANs are generally used to allow administrators to manage their resources easily.

How Does Inter-VLAN Routing Work?

Now that we understand what a VLAN is and why it is used, it is important to note that a VLAN is an isolated network, and if we wish to communicate outside of it, we will need to set up an Inter-VLAN route. A route allows VLANs to communicate via virtual links with each other. This can be done by using both hardware and software with such methods as routers, switches with layer-3 (routing) functionality, or VLAN trunks. This way you can create dedicated subnets for any specific purpose you may have, such as IoT devices, guest networks, or applications that require specific configuration. Once accomplished, your network architecture will have the necessary flexibility to account for any changes and growth that come along the way. Your control will be granular, and precise, and you will also have separation between network traffic for added security.

What Are the Different Types of Inter-VLAN Routing?

There are three types of Inter-VLAN Routing. They consist of Traditional Inter-VLAN Routing, Router-on-a-Stick Inter-VLAN Routing, and Multilayer Switch Inter-VLAN Routing. Traditional Inter-VLAN routing is archaic by today’s standards but still usable as a low-budget option. In this variation, each VLAN is connected to a separate router or Layer 3 switch that acts as the default gateway for the VLAN. Traditional Inter-VLAN routing requires a separate interface on the router or Layer 3 switch for each VLAN. This process drastically skyrockets in network complexity and scales very poorly. This is why the other two methods are considerably better unless you are on an extreme budget and need to manage a small network. In Router-on-a-Stick Inter-VLAN Routing, you only need a single router or Layer 3 switch to use as the default gateway for all VLANs. However, similarly to the traditional Inter-VLAN routing, it requires a separate interface on the router or Layer 3 switch for every VLAN. There is a difference, however, and that is the fact that this method doesn’t require different physical interfaces for each VLAN, instead it uses subinterfaces on a single physical interface. This effectively reduces network complexity and makes it easier to manage. Lastly, we have the Multilayer Switch Inter-VLAN Routing. This approach uses a Layer 3 switch as the default gateway for all VLANs. The Layer 3 switch effectively operates as both a router and switch, functioning as a universal device that can freely change between routing and switching tasks. This helps the network become more manageable in comparison to the previous two types, and far less complex. This in turn means that you can add new VLANs without needing any additional hardware, allowing for far greater scalability.

Which Type of Inter-VLAN Routing Should I Use?

Figuring out which Inter-VLAN Routing type you should use depends on a multitude of factors, we will cover the most common use cases so you can better understand which system you should implement for the most optimal results. Firstly, Traditional Inter-VLAN Routing is typically used in networks with a small amount of VLANs and a tight budget. This way everything is simple and easy to manage. The only concern is if you ever need to expand your network, scaling it up will be a huge issue as the number of VLANs increases. Router-on-a-Stick Inter–VLAN Routing is the medium option. If you have a large number of VLANs but the hardware budget is limited, this is likely the option for you. It is more complex to set up than the Traditional type, but it offers far greater control over your VLAN routing policies. It is a great compromise between Traditional Inter-VLAN Routing and getting a full Layer 3 switch. Lastly, we have the Multilayer Switch Inter-VLAN Routing. It is predominantly used by large enterprises and data centers. This is due to the fact that for large-scale VLAN use, there is an expectation of high performance and security which the Multilayer Switch Inter-VLAN Routing is able to provide. In summary, Traditional Inter-VLAN Routing is a simple, affordable option for small networks. The Router-on-a-Stick approach is a cost-effective option for larger networks with a small hardware budget, and Multilayer Switch Inter-VLAN Routing is ideal for large, enterprise-level networks.

Setting up Your Inter-VLAN Routing

There are many different ways that you can set up your routing, from software to hardware options, as we previously mentioned. We’re going to go through a relatively simple process that should be applicable to Cisco devices. Hopefully, the instructions will be relevant enough to you to successfully do this task.

1. Log into the web-configuration panel in your browser by typing in your local IP. Log in using the adequate credentials, if you haven’t changed them, check the default credentials for your device.
2. To create VLANs, navigate to VLAN settings under the VLAN management tab, note that you may have to select the advanced mode on a dropdown menu to get full access to the configurations, usually located in the top right corner.
3. You should already have VLAN 1 created by default, click on add to create the 2nd VLAN. Give it a name and finalize the creation.
4. You need to assign ports to these VLANs, to do this, navigate to Port VLAN Membership. The default should be that all of the ports are set to the 1st VLAN which was already pre-made. Click on the second VLAN, then click on “Join VLAN”.  Under Access VLAN ID, Native VLAN ID, and General PVID, set it to VLAN 2.
5. Now you need to assign an IP address to each of the VLANs. To do this, navigate to IP Configuration, in the dropdown menu click on IPv4 Interface, then click “Add”. Pick VLAN1, check the Static IP box, put 10.1.1.1 as the IP address, and set the prefix length to 24. Do the same process for VLAN2 except input the IP as 10.2.2.1, and click “Apply”.
6. You can also configure the DHCP server for auto-VLANs if you wish. You can do this under the “Network Pools” tab under IP Configuration.
7. Finally, you can connect the desired PCs to their respective VLANs under their Local Area Network Properties tab for each respective VLAN, setting them under IPv4 to automatically discover both IP and DNS settings. This is done in the adapter settings for your PC.
8. If everything has been done correctly, under the IP Configuration tab in the browser, under the Address Binding Table, you should see both PCs assigned their respective VLANs.
9. Finally, you can ping the assigned IP addresses in your Command Terminal to check that they are in fact working and connected.

Summary

Hopefully, this article has been useful in helping you understand VLANs better. We have covered the basics of what a VLAN is, why and how it is used, as well as its different types. It allows you to manage your networks more easily, allowing for greater control and precision, as well as potentially saving costs.