The Carrier Board Design Guide and the Aster Eval Board have pin 191 (ETH_GND) connected directly to common ground but the Colibri Evaluation board has it connected to common ground through a filter. See attached images ( [upload|3Czn76V2NdLfdVm5y5+S2CJMPCk=], [upload|2jZUbqI8QaF5UlVb0CIyEd41qZM=], [upload|lmzL7qB4+3ys+bXO6L2jG8u3gEY=] ).
It is recommended to connect the SODIMM_191 to the common Ground (GND) as done on the Aster Carrier Board.
On Colibri Evaluation Board Schematics, please refer to NOTE 2 on the Ethernet Schematic Page