• List of NuGet packages and version that you are using:
• Runtime version (e.g. net461, net48, netcoreapp2.1, netcoreapp3.1, etc. You can find this information from the *.csproj file):
• Hosting environment (e.g. Azure Web App, App Service on Linux, Windows, Ubuntu, etc.):

Describe the bug

A clear and concise description of what the bug is.

X-Forwarded-For is specified with an IPv6 IP address and we return just the first 4 characters.

• X-Forwarded-For : 180.60.62.8:36608 becomes 180.60.62.8
• X-Forwarded-For : 2400:4151:f82:3000:8d8:f068:5c34:824, 147.243.22.167:52155 becomes 2400

There is an inconsistency between the ASP NET and .NET Core implementations:

• Core

  ApplicationInsights-dotnet/NETCORE/src/Microsoft.ApplicationInsights.AspNetCore/TelemetryInitializers/ClientIpHeaderTelemetryInitializer.cs

  Line 159 in 3b15e65

  private string GetIpFromHeader(string clientIpsFromHeader)

• AspNet

  ApplicationInsights-dotnet/WEB/Src/Web/Web/ClientIpHeaderTelemetryInitializer.cs

  Line 106 in 3b15e65

  private static string CutPort(string address)

One uses LastIndexOf and other other uses IndexOf to find the : character.