Adding a Host to System Center Virtual Machine Manager 2008 (SCVMM 2008) fails with a variation of Error (2916):
VMM is unable to complete the request. The connection to the agent ServerA.contoso.com was lost.
(The WinRM client cannot complete the operation within the time specified. Check if the machine name is valid and is reachable over the network and firewall exception for Windows Remote Management service is enabled. (0x80338126))
Ensure that the WS-Management service and the agent are installed and running and that a firewall is not blocking HTTP traffic. If the error persists; reboot ServerA.contoso.com and then try the operation again.
Test multiple communication protocols between the two systems; the SCVMM 2008 Server and Host in this example. Some firewalls can have content filtering enabled despite showing that it is not. Remove all non-Windows software firewalls and bypass all hardware appliance firewalls entirely long enough to perform testing to verify whether or not they are contributing to the problem.
The following tests are examples of protocols that should always succeed. Test both directions always:
WinRM successful reply example:
C:\>winrm id -r:ServerA
ProtocolVersion = http://schemas.dmtf.org/wbem/wsman/1/wsman.xsd
ProductVendor = Microsoft Corporation
ProductVersion = OS: 6.1.7600 SP: 0.0 Stack: 2.0
Recently a firewall appliance sold by a major vendor showed content filtering disabled and not licensed to be turned on, yet was still filtering specific content. This was discovered through examination of network traces. Do not assume content, protocols or traffic are not being blocked. Perform tests to verify.