As businesses continue to migrate infrastructure to the cloud, networking concepts that were once strictly physical like VLANs and subnets have evolved. While these terms are often used interchangeably, especially in cloud native discussions, they serve distinct purposes.
This guide will clarify the differences between VLANs and subnets, highlight how they’re implemented in cloud environments like Azure and AWS, and explain how each plays a role in designing secure, scalable, and logically segmented cloud networks. Understanding these distinctions is essential for any cloud engineering initiative.
Quick Definitions
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VLAN (Virtual Local Area Network): A method of logically segmenting a Layer 2 network without requiring separate physical hardware.
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Subnet (Subnetwork): A Layer 3 IP level segmentation technique used to divide a larger IP address space into smaller, routable units.
In traditional on-prem environments, VLANs and subnets often go hand in hand. In the cloud, however, their implementations differ significantly, especially since cloud providers do not expose Layer 2 infrastructure to customers.
Core Conceptual Differences
How VLANs Work (Traditionally)
In an on premises network, a VLAN allows you to create logically separate groups of devices on the same physical switch. This reduces broadcast traffic and isolates traffic between departments (e.g., accounting and sales). VLANs are enforced using tags (802.1Q) that tell switches how to route frames.
In the cloud, you do not manage Layer 2 directly, so traditional VLAN tagging is not available. Instead, similar functionality is achieved through network security groups, routing tables, and virtual network peering.
How Subnets Work (Traditionally and in the Cloud)
A subnet divides a larger IP network into smaller, addressable segments. Each subnet has its own IP range and typically acts as a separate routing boundary. This is true both on prem and in the cloud.
In the cloud, subnets are the primary method of network segmentation. Whether you’re using Azure, AWS, or GCP, you create subnets within a virtual network (VNet or VPC) to organize resources and apply policies.
For example, in Azure:
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A VNet contains multiple subnets.
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Each subnet is associated with routing tables and NSGs.
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Traffic between subnets is routed at Layer 3 and can be controlled using rules.
VLANs in the Cloud: Are They Still Relevant?
Most cloud providers abstract away VLANs completely. Instead of configuring VLAN IDs and switches, you use constructs like:
These constructs mimic VLAN isolation behavior by allowing or denying traffic between subnetworks, even within the same VNet or VPC.
Some hybrid cloud or private cloud deployments (e.g., using Azure Stack HCI or VMware Cloud) still use VLANs to segment traffic between on prem and cloud-connected systems, but this is less common in fully managed, public cloud deployments.
When to Use Subnets vs VLAN-Like Controls in the Cloud
Use Subnets When You Need:
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Clear separation of services (e.g., database subnet, application subnet)
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Different routing or NAT rules
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Deployment of services across availability zones
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Public vs private resource separation
Use VLAN-Like Controls When You Need:
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Port level traffic isolation
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Microsegmentation between workloads in the same subnet
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Enforcement of security policies based on source/destination
Security and Compliance Considerations
Proper network segmentation is a cornerstone of security and compliance in the cloud. Here are key considerations:
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Subnets allow fine grained control of traffic flow using route tables and NSGs.
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Application-level segmentation using NSGs or Azure Firewall is critical in the absence of VLANs.
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Zero Trust Architecture often involves multiple subnet segments with limited interconnectivity even if those segments reside within the same VNet.
Summary: What You Should Know
FAQs
1. What is the difference between a VLAN and a subnet in cloud networking? A VLAN operates at Layer 2 (data link) and logically segments devices on the same physical network, while a subnet operates at Layer 3 (network) and divides an IP address space into smaller routable segments. In the cloud, providers abstract away Layer 2 entirely, so subnets within a VNet or VPC are the primary segmentation method. VLAN-like isolation is achieved through security groups and firewall rules rather than traditional VLAN tagging.
2. Do AWS and Azure support VLANs? AWS and Azure do not expose traditional VLAN tagging to customers within their public cloud environments. Instead, they offer subnets within VPCs (AWS) and VNets (Azure) for network segmentation, along with security groups and network security groups to control traffic flow. VLANs may still be relevant in hybrid scenarios that use dedicated connections like AWS Direct Connect or Azure ExpressRoute.
3. How do I segment my cloud network without VLANs? In the cloud, you segment networks by creating multiple subnets within a virtual network and applying security controls to each. Use network security groups (NSGs) or security groups to restrict traffic between subnets, and configure route tables to control how traffic flows. For microsegmentation within a subnet, consider application-level firewalls such as Azure Firewall or AWS Network Firewall.
4. Should I use VLANs or subnets when migrating to the cloud? For most cloud migrations, subnets are the correct approach since cloud providers are built around Layer 3 segmentation. If you are running a hybrid environment that bridges on-premises infrastructure with the cloud, you may still use VLANs on the on-prem side while mapping them to subnets and security groups in the cloud. A well-planned migration will translate your existing VLAN-based segmentation strategy into cloud-native subnet and security group configurations.
How Exodata Can Help
At Exodata, we specialize in cloud network architecture and managed IT services for organizations modernizing their infrastructure. We help small and mid sized businesses:
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Design cloud-native network topologies using VNets and subnets
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Configure secure connectivity across hybrid or multi cloud environments
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Implement access control using NSGs, firewalls, and zero trust principles
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Replace legacy VLAN strategies with cloud-ready segmentation
Whether you’re starting from scratch or migrating from a physical data center, we ensure your cloud network is secure, performant, and maintainable.
Get your cloud network architecture right from the start. Exodata helps businesses design secure, scalable networks that replace legacy VLAN strategies with modern cloud-native segmentation. Contact us to discuss your cloud networking needs with our engineering team.