When you deploy infrastructure in a public cloud environment like Azure, AWS, or Google Cloud, one of the foundational pieces of networking you’ll encounter is the route table.
Route tables define how network traffic flows between different parts of your environment whether between subnets, virtual networks, the internet, or private resources like VPNs and firewalls. Done right, they enable controlled, efficient, and secure communication across cloud workloads. Done wrong, they can cause application failures, security risks, or service disruptions.
This post breaks down what route tables are, how they work in cloud environments, and what best practices businesses should follow. Whether you manage routing in-house or rely on managed IT services, understanding route tables is essential.
What Is a Route Table?
A route table is a set of rules (routes) that determine where network traffic is sent based on the destination IP address.
Each rule in the table consists of:
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Destination: The IP address range the route applies to (e.g.,
10.1.0.0/16,0.0.0.0/0) -
Next hop: Where traffic is forwarded (e.g., a virtual appliance, internet gateway, or another subnet)
In traditional networks, this logic exists in routers and firewalls. In the cloud, you define these routing behaviors directly at the subnet or network interface level using cloud-native route tables.
How Route Tables Work in Azure and AWS
Azure
In Microsoft Azure, route tables are called User-Defined Routes (UDRs) and are associated with subnets in a Virtual Network (VNet).
Default behavior:
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Azure automatically creates system routes that allow communication within the VNet.
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Internet traffic is routed through a default gateway.
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You can override or add routes using custom UDRs.
Common next hop types in Azure:
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Virtual network gateway (for VPNs)
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Internet
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Virtual appliance (e.g., firewall or NVA)
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None (drop the traffic)
AWS
In Amazon Web Services, each VPC (Virtual Private Cloud) has one or more route tables that you associate with subnets.
Default behavior:
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A main route table is automatically created for every VPC.
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Routes to other subnets in the VPC are included by default.
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You add custom routes for VPNs, NAT gateways, or peered VPCs.
Common next hops in AWS:
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Local (within the VPC)
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Internet Gateway
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NAT Gateway
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Virtual private gateway (for VPNs)
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VPC peering connection
Google Cloud
Google Cloud uses a similar concept called routes, which are applied at the VPC network level. Like Azure and AWS, Google Cloud automatically creates system-generated routes for subnet-to-subnet communication and provides the ability to define custom static and dynamic routes for more advanced traffic steering.
Why Route Tables Matter in the Cloud
In cloud environments, routing is no longer something abstract that “just works.” You are expected to define your network architecture intentionally. This is a core part of cloud engineering and requires careful planning alongside your broader security and compliance strategy.
Use cases include:
- Controlling egress to the internet
- Directing traffic through a firewall or proxy
- Hybrid connectivity
- Spoke-to-spoke VNet communication
Common Routing Scenarios
Troubleshooting Tip
Route table misconfigurations are a common cause of cloud networking issues. If a VM or service can’t reach a destination:
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Check the route table associated with the subnet
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Ensure there’s a specific route to the destination
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Validate the next hop is reachable
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Confirm NSGs or security groups are not blocking traffic
Best Practices
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Keep route tables simple: Avoid unnecessary complexity unless your architecture requires it
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Use naming conventions: Identify route tables by purpose (e.g.,
RT-Web,RT-DB,RT-Spoke1) -
Isolate sensitive traffic: Send certain subnets through firewalls or inspect outbound flows
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Audit changes: Use change tracking or automation to manage route modifications
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Test connectivity: Use
ping,tracert, or tools like Azure Network Watcher or AWS VPC Reachability Analyzer
Frequently Asked Questions
What is a route table in cloud networking?
A route table is a set of rules that tells a cloud network where to send traffic based on its destination IP address. Every subnet in a virtual network (whether in Azure, AWS, or Google Cloud) is associated with a route table. The table contains entries that pair a destination address range with a next hop, which is the next network resource the traffic should be forwarded to. Cloud providers create default route tables automatically, and administrators can add custom routes to control traffic flow more precisely.
How do route tables work in Azure?
In Azure, route tables work through a combination of system routes and User-Defined Routes (UDRs). Azure automatically generates system routes that handle basic communication within a Virtual Network (VNet), to the internet, and between peered VNets. When you need to override this default behavior — for example, to send all outbound traffic through a firewall appliance — you create a custom route table with UDRs and associate it with one or more subnets. The route with the longest matching prefix always takes priority, and UDRs override system routes when their prefixes match.
What is the difference between system routes and custom routes?
System routes are created and managed automatically by the cloud provider. They handle fundamental connectivity such as routing between subnets in the same virtual network and providing a default path to the internet. Custom routes (called User-Defined Routes in Azure or simply custom routes in AWS) are manually created by administrators to override or extend this default behavior. Common use cases for custom routes include forcing traffic through a network virtual appliance, blocking internet access from certain subnets, or directing traffic to a VPN gateway for hybrid connectivity.
Why is route table misconfiguration a common cause of outages?
Route tables operate at a foundational layer of cloud networking. A single incorrect entry — such as a missing route, a wrong next hop, or an overly broad destination prefix — can silently redirect or drop traffic across an entire subnet. Because route table changes often do not produce immediate error messages, misconfigurations can go undetected until applications or services begin to fail. This is why auditing route changes, using infrastructure as code, and testing connectivity after every modification are considered essential best practices.
How Exodata Helps
At Exodata, we help businesses design and manage secure, reliable cloud networks. Whether you’re migrating to Azure or AWS, or optimizing your existing environment, our experts ensure your routing is intentional, predictable, and compliant.
We offer:
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Cloud network architecture assessments
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Secure routing design for hub-and-spoke or hybrid networks
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Firewall and virtual appliance routing implementation
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Automated deployments using infrastructure as code through our DevOps and infrastructure services
Ready to get your cloud routing right? Whether you need a network architecture assessment, help migrating to Azure or AWS, or ongoing support for your hybrid environment, Exodata’s team is here to help. Contact us today to discuss how we can streamline your cloud networking with confidence.