By the way, we don't do fancy stuff with the network configuration apart from the setting the gateway.
You can take a look into /etc/network/interfaces to see how eBox sets the configuration.
What we do in a different way is setting the gateways, to make them work with a multipath configuration we add them to the default table instead of adding them to the main table.
You can still list the default gateway by running:
ip route ls table default
route is the past ip route is the future
Jokes apart, please ask again if you have more troubles, I'll be delighted to help you with the eBox configuration.