Traffic Manager subnet override using Azure CLI

Article
06/03/2024

Traffic Manager subnet override allows you to alter the routing method of a profile. The addition of an override directs traffic based upon the end user's IP address with a predefined IP address range to endpoint mapping.

How subnet override works

When subnet overrides are added to a traffic manager profile, Traffic Manager first checks if there's a subnet override for the end user’s IP address. If one is found, the user’s DNS query ix directed to the corresponding endpoint. If a mapping is not found, Traffic Manager falls back to the profile’s original routing method.

The IP address ranges can be specified as either CIDR ranges (for example, 1.2.3.0/24) or as address ranges (for example, 1.2.3.4-5.6.7.8). The IP ranges associated with each endpoint must be unique to that endpoint. Any overlap of IP address ranges among different endpoints causes the profile to be rejected by Traffic Manager.

There are two types of routing profiles that support subnet overrides:

Geographic - If Traffic Manager finds a subnet override for the DNS query's IP address, it routes the query to the endpoint whatever the health of the endpoint is.
Performance - If Traffic Manager finds a subnet override for the DNS query's IP address, it only routes the traffic to the endpoint if it's healthy. Traffic Manager falls back to the performance routing heuristic if the subnet override endpoint isn't healthy.

Note

Azure Traffic Manager supports IPv6 addresses in subnet overrides for subnet profiles. This capability enables more granular control over traffic routing based on the source IP address of DNS queries, including both IPv4 and IPv6 addresses.

Create a Traffic Manager subnet override

To create a Traffic Manager subnet override, you can use Azure CLI to add the subnets for the override to the Traffic Manager endpoint.

Prerequisites

Use the Bash environment in Azure Cloud Shell. For more information, see Quickstart for Bash in Azure Cloud Shell.
If you prefer to run CLI reference commands locally, install the Azure CLI. If you're running on Windows or macOS, consider running Azure CLI in a Docker container. For more information, see How to run the Azure CLI in a Docker container.
- If you're using a local installation, sign in to the Azure CLI by using the az login command. To finish the authentication process, follow the steps displayed in your terminal. For other sign-in options, see Sign in with the Azure CLI.
- When you're prompted, install the Azure CLI extension on first use. For more information about extensions, see Use extensions with the Azure CLI.
- Run az version to find the version and dependent libraries that are installed. To upgrade to the latest version, run az upgrade.

This article requires version 2.0.28 or later of the Azure CLI. If using Azure Cloud Shell, the latest version is already installed.

Update the Traffic Manager endpoint with subnet override.

Use Azure CLI to update your endpoint with az network traffic-manager endpoint update.

### Add a range of IPs ###
az network traffic-manager endpoint update \
    --name MyEndpoint \
    --profile-name MyTmProfile \
    --resource-group MyResourceGroup \
    --subnets 1.2.3.4-5.6.7.8 \
    --type AzureEndpoints

### Add a subnet ###
az network traffic-manager endpoint update \
    --name MyEndpoint \
    --profile-name MyTmProfile \
    --resource-group MyResourceGroup \
    --subnets 9.10.11.0:24 \
    --type AzureEndpoints

You can remove the IP address ranges by running the az network traffic-manager endpoint update with the --remove option.

az network traffic-manager endpoint update \
    --name MyEndpoint \
    --profile-name MyTmProfile \
    --resource-group MyResourceGroup \
    --remove subnets \
    --type AzureEndpoints

Next Steps

Learn more about Traffic Manager traffic routing methods.

Learn about the Subnet traffic-routing method

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