Azure User Defined Routes: A Comprehensive Guide

Azure User Defined Routes offer a flexible way to control traffic flow between subnets and virtual networks.

This flexibility is achieved through the use of routes that are defined by users, allowing for more granular control over network traffic.

Azure User Defined Routes can be used to route traffic from a virtual network to a subnet, or from one subnet to another.

To create a User Defined Route, you'll need to specify the destination IP address, the next hop IP address, and the action to take when the route is matched.

These routes can be used to control traffic flow in a variety of scenarios, such as routing traffic from a virtual network to an on-premises location.

To create user defined routes, you need to create a routing configuration and rule collection with routing rules. This involves defining the UDRs for the network group by creating a routing configuration and rule collection with routing rules.

You can create a routing configuration by returning to the Virtual Network Manager instance and Configurations under Settings, selecting + Create or Create routing configuration, and entering or selecting the required information. The name of the routing configuration should be "routing-configuration".

A rule collection is a collection of routing rules that are applied to a network group. To create a rule collection, select the Rule collections tab or Next: Rule collections >, and then select + Add. In the Add a rule collection section, enter or select the required information, including the name, description, and target network groups.

You can add a routing rule by selecting + add under Routing rules, and then entering or selecting the required information, including the name, destination, and next hop. The destination type should be IP address, and the destination IP addresses/CIDR ranges should be "0.0.0.0/0".

When creating a routing rule, you need to consider the impact of existing routing rules. For more information, see Impacts of user-defined routes.

Here's a summary of the steps to create a routing configuration and rule collection:

Once you have created a routing configuration and rule collection, you can deploy the routing configuration to create the UDRs for the network group. This involves selecting the checkbox for the routing configuration and choosing Deploy from the taskbar.

When deploying a routing configuration, you need to specify the target regions and include user-defined routing configurations in your goal state.

Route tables are a crucial part of Azure user defined routes, allowing you to control network traffic flow in your Azure environment.

To create a route table, search for "Route Tables" in the Azure Portal and click on "Add". Provide a name, select a resource group and a region where your routing table should be created.

A route table can be associated with one or more subnets, and each subnet can only be associated with a single route table. Subnets rely on system routes until a route table is associated with them.

To define a route, navigate to the "Routes" section in your route table and click on "Add". You must provide a name for the route, an address prefix, and the next hop type.

The next hop type determines where the traffic is sent, and there are several options to choose from:

IP forwarding must be enabled on the network card for traffic to take place. The easiest way to do this is by searching for your VM, clicking on "Networking", and enabling "IP forwarding" in the "IP configurations" section.