The U.S. Geological Survey (USGS) National Strong Motion Project (NSMP) operates numerous strong-motion seismographs to monitor ground shaking and structural response caused by large, nearby earthquakes. This report describes a problem NSMP scientists encountered communicating over the Internet with several Kinemetrics, Inc., Granite strong-motion recorders.
The Granite strong-motion recorders (“Granites”) get into a state where they cannot be reached from the Internet and they cannot reach the Internet, yet they can reach and be reached from the local Ethernet subnet. The reason is that the Internet Protocol (IP) network default route has disappeared; only the local route is available. Diagnosis is complicated by the unpredictability of the circumstances leading to the failure. The failures have happened at several field sites but cannot be reproduced in the lab.
This report describes the IP networking behavior of a Granite system and provides modifications to the Granite Ethernet device drivers to send Ethernet link (carrier) state-change event notifications to the Linux kernel. With these modifications, the Linux netplugd daemon can be configured to properly reconfigure Granite IP networking when the Ethernet interface link state changes.
