This counter tracks received UDP datagrams that could not be delivered for reasons other than a missing listening application, such as buffer or checksum problems. Administrators use it to detect resource exhaustion or corruption affecting inbound UDP traffic on the virtual router, distinct from simple no-listener cases tracked elsewhere. For example, a jump in csOrionVPNVRouterUdpInErrors during a period of heavy SNMP polling load suggests the VR's UDP receive buffers are being overrun rather than the poller simply targeting the wrong port.