Hello,
we use the SJA1105 in our product as automotive switch. There is a schematic of this device:
Zapojení switch.png
The device works reliably, but the problem occurs if the device is accessed not directly from the PC but by the Ethernet switch connected to the RJ-45 port. In this case, the device will stop responding and the connected switch will also stop routing communication between devices connected to it. If I connect to the device via the T1 port (via Media Convertor), then everything works well. We found that no matter the RGMII speed (1000/100) neither works. For configuration, we use the modified example cfg_applicationBoard.py (attached bellow). The problem also occurs if we connect two 100BASE-T1 MG devices to each other via an RJ-45 port. In this case, we will also lose access to both devices. I assume that the problem will be in the configuration of the switch. The weird thing is that this happens only on the port that is connected via RGMII.