I'm facing an issue while configuring VNet Integration for an Azure Function App (Premium Plan).

Nagendra Matharasi 20 Reputation points
2026-01-21T21:39:39.1166667+00:00
  • When a NAT Gateway is attached to the integration subnet, VNet integration for the Function App fails with the error: “Delegated subnet cannot be attached to StandardV2 NAT Gateway.”
  • When I remove the NAT Gateway from the subnet, the Function App is able to successfully add and connect to the VNet.
  • However, in this scenario, outbound traffic uses a default dynamic Azure IP instead of the required static IP.
Azure Functions
Azure Functions

An Azure service that provides an event-driven serverless compute platform.

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Answer accepted by question author
Rakesh Mishra 11,440 Reputation points Microsoft External Staff Moderator
2026-01-22T00:36:58.2933333+00:00

Hi @Nagendra Matharasi ,

Welcome to the Microsoft Q&A Platform! Thank you for asking your question here.

Root cause

The error “Delegated subnet cannot be attached to StandardV2 NAT Gateway” is caused by a limitation in StandardV2 NAT Gateway: StandardV2 cannot be attached to delegated subnets for several Azure services - including Azure Web Apps / App Service (the service behind Functions’ VNet integration).

In other words, the integration subnet for a Function/App is a delegated subnet (Microsoft.Web), and StandardV2 currently isn’t supported on that kind of delegated subnet.

Possible solution
  1. Use a Standard (v1) NAT Gateway attached to the integration subnet. Standard (v1) NAT gateway is compatible with App Service / Function VNet integration and will provide a static outbound IP. This is the simplest, doc-recommended approach.
  2. If you require StandardV2 features (zone redundancy / IPv6) — at present you cannot attach a StandardV2 NAT to an App Service / delegated subnet. Options are:
    • Re-evaluate whether you can accept Standard (v1) NAT (recommended).
    • Use an alternate egress architecture (for example, funnel outbound through an Azure Firewall/egress appliance in a hub and use UDRs), but that is more complex and changes your design.

Note: You must also enable Route All for the webapp/function VNET integration so outbound traffic is sent to the VNET routes.

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