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BugZero found this defect 2559 days ago.
A Veeam Agent for Microsoft Windows backup job with the following error message:
This error message relates to a failure to establish communication with the Veeam Agent for Microsoft Windows service. If the Veeam Agent for Microsoft Windows service is confirmed as running, there may be a firewall issue. This article specifically documents a situation in which the Veeam Agent for Microsoft Windows service cannot start, or gets stuck starting, due to a port conflict. The Veeam Agent for Microsoft Windows service default is port 6183. As the service starts it will check if that port is in use, and if in use the service will increment and check again (6184,6185, etc.). It will attempt to increment up to 10 times before failing. (Logging example available below) A much rarer scenario is one in which the port Veeam Agent for Microsoft Windows service attempts to start on is registered in RPC Endpoint mapper by another process but is not actively in use. The service will not detect the port as in use and attempt to start, it will fail to start and will not increment the port it attempts to start on.
The following registry value may be used to force the Veeam Agent for Microsoft Windows service to start on a specific port. This registry value should be created on the machine where Veeam Agent for Microsoft Windows is installed. Key Location: HKLM\SOFTWARE\Veeam\Veeam Endpoint Backup\Value Name: EndPoint_Rpc_Transport_PortValue Type: DWORD (32-bit) ValueValue Data(Dec): <available_port>* *For the Value data, specify an available idle port. Start the Veeam Agent for Microsoft Windows service after putting the registry value in place. If the service is stuck in a starting state, forcibly stop the service process.