The two interfaces of M64 and M68
The M64 have two interfaces, called eth0 and eth1. eth0 is the interface with the on-board PHY while eth1 is the RGMII. By default eth0 is the primary interface, meaning that it has full TCP/IP functionality, while eth1 is the secondary, transparent, interface. However, you can define which interface should be primary by changing the TCPIP environment variable in the system.ini file. The default setting is
setenv TCPIP eth0
To use the RGMII as the primary interface with full TCP/IP functionality, set the system.ini script file as follows:
setenv TCPIP eth1
For M64 only the primary interface has an IP address and supports MDIO commands. The secondary interface is transparent. If two separate interfaces are needed, a M68 is required. For more information, read section 8.4 in the M64 Design Manual.
On M68 both interfaces, eth0 and eth1 have full TCP/IP functionality. Just as on M64, eth0 is the interface with the on-board PHY while eth1 is the RGMII. By default, both of these are enabled. However, you can define either one as a primary interface in the system.ini file, but this will make the other interface secondary, effectively turning your M68 into a M64. Default setting on M68 is
setenv TCPIP both
If both interfaces are enabled, eth0 is mapped to enet0 and eth1 to enet1. If only one interface is enabled, the primary interface will be mapped to enet0 (and enet1 will not exist).