Nothing... just configure each interface, and add packet filters (for straight routing, an any-any-any rule would suffice). You can add static routes, etc. to direct traffic at other gateways as needed. If you are connecting to the internet, you will need to use some form of NAT though.
so not work for me, i need use astaro as default gateway on my local net and it conect to other networks, i have configure each interfaces and added an any-any-any to packet filter by now.