A Tale of Two Network Interfaces
Two NICs, one subnet. Seems fine. It isn’t. I frequently run into this on Linux servers, PTP Grandmaster clocks, telemetry acquisition and analysis servers, industrial controllers and other appliances where Linux is running under the hood whether the vendor advertises it or not. Most of them cover this limitation somewhere in their published documentation. It is worth reading before you plug in the second cable. The symptoms are always the same: traffic arrives on one interface, replies leave on another, sessions drop for no apparent reason, and nothing in the logs explains it. ...