I contacted the support and seems like someone in France wrote the instructions for configuring the network:
http://guides.ovh.net/OpenSolarisZones (no translation available currently).
I didn't manage to get the zone working so i just entered the last three commands and everything seems to work just fine:
ifconfig e1000g0 IP.FAIL.OVER netmask 255.255.255.255 broadcast + up
route add HOST.SERVER.IP.0/24 IP.FAIL.OVER -interface -ifp e1000g0
route add default HOST.GATEWAY.IP