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Document IPNetwork and ForwardedHeadersOptions.KnownNetworks obsolescence for .NET 10 #47899

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5 changes: 3 additions & 2 deletions docs/core/compatibility/10.0.md
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Expand Up @@ -17,11 +17,12 @@ If you're migrating an app to .NET 10, the breaking changes listed here might af

## ASP.NET Core

| Title | Type of change | Introduced version |
|-------|-------------------|--------------------|
| Title | Type of change | Introduced version |
|-------|---------------------|--------------------|
| [Deprecation of WithOpenApi extension method](aspnet-core/10/withopenapi-deprecated.md) | Source incompatible | Preview 7 |
| [IActionContextAccessor and ActionContextAccessor are obsolete](aspnet-core/10/iactioncontextaccessor-obsolete.md) | Source incompatible/behavioral change | Preview 7 |
| [IncludeOpenAPIAnalyzers property and MVC API analyzers are deprecated](aspnet-core/10/openapi-analyzers-deprecated.md) | Source incompatible | Preview 7 |
| [IPNetwork and ForwardedHeadersOptions.KnownNetworks are obsolete](aspnet-core/10/ipnetwork-knownnetworks-obsolete.md) | Source incompatible | Preview 7 |
| [Microsoft.Extensions.ApiDescription.Client package deprecated](aspnet-core/10/apidescription-client-deprecated.md) | Source incompatible | Preview 7 |

## Containers
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50 changes: 50 additions & 0 deletions docs/core/compatibility/aspnet-core/10/ipnetwork-knownnetworks-obsolete.md
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---
title: "Breaking change: IPNetwork and ForwardedHeadersOptions.KnownNetworks are obsolete"
description: Learn about the breaking change in ASP.NET Core 10.0 where IPNetwork and ForwardedHeadersOptions.KnownNetworks have been obsoleted in favor of System.Net.IPNetwork and KnownIPNetworks.
ms.date: 08/08/2025
ai-usage: ai-assisted
ms.custom: https://github.com/aspnet/Announcements/issues/523
---
# IPNetwork and ForwardedHeadersOptions.KnownNetworks are obsolete

<xref:Microsoft.AspNetCore.HttpOverrides.IPNetwork?displayProperty=fullName> and <xref:Microsoft.AspNetCore.Builder.ForwardedHeadersOptions.KnownNetworks> have been marked as obsolete in favor of using <xref:System.Net.IPNetwork?displayProperty=fullName> and `KnownIPNetworks`.

## Version introduced

.NET 10 Preview 7

## Previous behavior

Previously, you could use <xref:Microsoft.AspNetCore.HttpOverrides.IPNetwork?displayProperty=fullName> and <xref:Microsoft.AspNetCore.Builder.ForwardedHeadersOptions.KnownNetworks> to configure known networks for the forwarded headers middleware:

```csharp
app.UseForwardedHeaders(new ForwardedHeadersOptions
{
KnownNetworks.Add(new(IPAddress.Loopback, 8))
});
```

## New behavior

Starting in .NET 10, if you use [the obsolete APIs](#affected-apis) in your code, you'll get warning `ASPDEPR005` at compile time:

> warning ASPDEPR005: Please use KnownIPNetworks instead. For more information, visit <https://aka.ms/aspnet/deprecate/005>.

Use the <xref:System.Net.IPNetwork?displayProperty=fullName> type and `KnownIPNetworks` property instead.

## Type of breaking change

This change can affect [source compatibility](../../categories.md#source-compatibility).

## Reason for change

<xref:System.Net.IPNetwork?displayProperty=fullName> has replaced the <xref:Microsoft.AspNetCore.HttpOverrides.IPNetwork?displayProperty=fullName> type that was implemented for <xref:Microsoft.AspNetCore.HttpOverrides.ForwardedHeadersMiddleware>.

## Recommended action

Change to using <xref:System.Net.IPNetwork?displayProperty=fullName> and `KnownIPNetworks`.

## Affected APIs

- <xref:Microsoft.AspNetCore.HttpOverrides.IPNetwork?displayProperty=fullName>
- <xref:Microsoft.AspNetCore.Builder.ForwardedHeadersOptions.KnownNetworks?displayProperty=fullName>
2 changes: 2 additions & 0 deletions docs/core/compatibility/toc.yml
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Expand Up @@ -16,6 +16,8 @@ items:
href: aspnet-core/10/iactioncontextaccessor-obsolete.md
- name: IncludeOpenAPIAnalyzers property and MVC API analyzers are deprecated
href: aspnet-core/10/openapi-analyzers-deprecated.md
- name: IPNetwork and ForwardedHeadersOptions.KnownNetworks are obsolete
href: aspnet-core/10/ipnetwork-knownnetworks-obsolete.md
- name: Microsoft.Extensions.ApiDescription.Client package deprecated
href: aspnet-core/10/apidescription-client-deprecated.md
- name: Containers
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