The GMAC at eth0 also works! :)
There is a good dual network test at apps/examples/bridge. There is a description in the Kconfig there. There are test configurations here:
boards/arm/sama5/sama5d3-xplained/configs/bridge boards/arm/sama5/sama5d4-ek/configs/bridgeThat should, at lease, show you how to configure the dual networks (and should even run on your board).
