When attempting to add or validate an Operating System (OS) connection, the following error may appear:
Could not connect to 192.168.0.1 or MYSERVER. RPC Server Unavailable (0x800706ba).  
The computer did not respond at all. This could be due to firewall blocking communication or WMI being disabled.
            | Cause ID | Description | 
|---|---|
| 1 (Most common) | Windows Firewall or network firewall is blocking the dynamic RPC response from the target host. RPC uses TCP ports 135/445 initially, then random dynamic ports (>1024) for return communication. The failure often occurs on the return channel. | 
| 2 | RPC or Remote Registry service is not running on the monitored host. | 
| 3 | NAT (Network Address Translation) device interfering with DCOM communication. RPC connections generally do not work reliably over NAT. | 
| 4 | System time between the Foglight Agent Manager (FglAM) and monitored host is not synchronized. | 
| 5 | IPSec policies on the monitored host restrict access to specific IPs, blocking the FglAM host connection. | 
| Solution ID | Action | 
|---|---|
| 1 | Enable Required Ports and Configure Firewall Rules (Recommended) Allow TCP ports on monitored host: • 135 (DCE/RPC Locator Service) • 139 (NetBIOS Session Service) • 445 (Windows Shares) • 49152–65535 (Dynamic RPC Ports) Enable firewall rules: netsh advfirewall firewall set rule group="Windows Management Instrumentation (WMI)" new enable=yes netsh advfirewall firewall set rule group="remote administration" new enable=yesOptional: Configure a static port for DCOM/WMI connections. Refer to KB 4289831 for details.  | 
| 2 | Start Required Services on Target Host Ensure the following services are running: • Remote Procedure Call (RPC) • Remote Registry See Microsoft KB 154596 for details.  | 
| 3 | Avoid NAT Devices Position the FglAM server on the same network segment as the monitored host to avoid RPC issues caused by NAT.  | 
| 4 | Synchronize System Clocks Verify system time on FglAM server matches that of the monitored host.  | 
| 5 | Revise IPSec Settings Confirm IPSec policies on monitored host allow traffic from the FglAM host IP address.  | 
Microsoft Technet "Troubleshooting The RPC Server is available"
http://social.technet.microsoft.com/wiki/contents/articles/4494.troubleshooting-the-rpc-server-is-unavailable.aspx
Here is some information on the ports for the WMI from our Agent Manager installation guide that should provide further information on the ports required for WMI.