All Linux monitored servers in a critical state is not an ideal way to start a Monday morning. Especially when none of the servers are actually experiencing an issue.

The issue at hand:
All of the Linux servers generated a heartbeat failure at the same time. Looking through the health explorer revealed the following error:

 The WinRM client cannot process the request because the server name cannot be resolved.

Testing WinRM with the following command also yielded the same result, and testing with DNS resolved the server name successfully.

winrm enumerate http://schemas.microsoft.com/wbem/wscim/1/cim-schema/2/SCX_OperatingSystem?__cimnamespace=root/scx -username:username -password:password -remote:https://servername:1270/wsman -auth:basic -skipCACheck -encoding:utf-8 -format:#pretty

The Solution:

WinRM uses the windows proxy to resolve host names, I checked the windows proxy settings on the Management Server using the following command.

netsh winhttp show proxy

and discovered that my proxy was set correctly but the bypass list for excluded servers had been replaced with a single server, using the below command I was able to amend the bypass list to include all of the local domain servers.

netsh winhttp set proxy proxy-server=”http=<proxy FQDN” bypass-list=”*<Domain Suffix>”

One that was completed the WinRM test returned the correct data and the servers started to turn green again.