I have a design with a tri-speed Base-T PHY, which exhibits some weird behaviour. For some reason sometimes the PHY doesn't establish the link with another PHY (typically in a PC) after the auto-negotiation. Some of my boards almost never fail, while others fail much more frequently.
I was wondering how people debug this kind of problems. Is there anything I can look up with a basic 500 MHz scope? Is there a low level protocol tester I could rent?