diff --git a/release-notes/2.1/Preview/2.1.0-preview2-known-issues.md b/release-notes/2.1/Preview/2.1.0-preview2-known-issues.md
index d2ac41da..936de39a 100644
--- a/release-notes/2.1/Preview/2.1.0-preview2-known-issues.md
+++ b/release-notes/2.1/Preview/2.1.0-preview2-known-issues.md
@@ -28,6 +28,12 @@ We have temporarily removed the Preview 2 installers from the Linux package feed
 sudo apt install dotnet-host=2.0.6-1
 ```
 
+## SocketsHttpHandler hangs on single core machines
+
+There is an issue with the new default HttpClientHandler that will cause hangs on single core machines when multiple connections are opened simultaneously. [corefx/issues/28979](https://github.com/dotnet/corefx/issues/28979). This issue has since been fixed, but is present in the Preview 2 build.
+
+**Workaround** - Use a machine with 2+ cores, or enable the older platform specific HttpClientHandler ([as described in the Preview 2 blog post](https://blogs.msdn.microsoft.com/dotnet/2018/04/11/announcing-net-core-2-1-preview-2/))
+
 ## Global Tools
 
 ### Global Tools targeting Preview or RC will not "roll-forward" to RTM
@@ -136,4 +142,4 @@ The `dotnet tool uninstall` command in Preview 2 cannot uninstall Global Tools t
 
 Preview 1 did not include an `uninstall` command.
 
-**Action -** Manually remove the shim and the implementation directory to uninstall any Preview 1 tools. The shim is in the `.dotnet\tools` directory and the implementation is in `.dotnet\toolspkgs`.
\ No newline at end of file
+**Action -** Manually remove the shim and the implementation directory to uninstall any Preview 1 tools. The shim is in the `.dotnet\tools` directory and the implementation is in `.dotnet\toolspkgs`.