In my Fibre Optic device (Linux 2.6.27, LXT971A PHY Transceiver), connection to the port is lost intermittently. While debugging with ETHtool, the following observation was observed:
Settings for eth0:
Supported ports: [ TP MII ]
Supported link modes: 10baseT/Half 10baseT/Full
Supported pause frame use: No
Supports auto-negotiation: Yes
Advertised link modes: 10baseT/Half 10baseT/Full
Advertised pause frame use: No
Advertised auto-negotiation: Yes
Link detected: yes
The Switch used (ruggedcom) supports only 100Mb/s FULL DUPLEX . Why is the speed moved to 1000Mb/s and the link detected is "yes" ? After this stage is reached the port will not try any other speed and stays in 1000Mb/s until device restart. Please note that the issue is observed only with a FO cable of length 30m or more and works fine with FO cable of length 2m.
Any comments or insights are greatly appreciated.