Fetching Instance Metadata from IMDS URL through App Service in VNet

Question

Is it possible to fetch instance metadata from the IMDS URL through an Azure App Service that is hosted on a VNet rather than a VM?

I attempted to retrieve instance metadata using the Kudu console of the App Service, but encountered the following error:

curl: (28) Failed to connect to 169.254.169.254 port 80 after 21050 ms: Could not connect to server.

The App Service is hosted on a subnet within the VNet, and a managed identity is enabled.

Answer 1

Hi @Joshi, Ritika
The Instance Metadata Service, or IMDS, works for Azure virtual machines and virtual machine scale sets. However, IMDS is not available from Azure App Services directly or even when App Services are sitting on a VNet. The error you encountered (curl: (28) Failed to connect to 169.254.169.254 port 80) occurs because the App Service cannot connect to the IMDS endpoint.
references:
https://learn.microsoft.com/en-us/azure/load-balancer/instance-metadata-service-load-balancer#retrieve-load-balancer-information-by-using-azure-instance-metadata-service
https://learn.microsoft.com/en-us/azure/virtual-machines/instance-metadata-service?tabs=windows#azure-instance-metadata-service
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