The UEC installer configures only one interface (one can choose manually which to configure), but eucalyptus needs more configuration if a front-end is using more than one interface. For example, if 'eth0' is connected to a public (user) facing network, and 'eth1' is connected to a node facing network, then VNET_PUBINTERFACE should be set to 'eth0' and VNET_PRIVINTERFACE should be set to 'eth1' in eucalyptus.conf in the eucalyptus-cc package. In addition, if a user chooses 'eth0' when installing, the avahi-publish process that gets started by eucalyptus-cc will not be broadcasting on eth1 when the user tries to install a node. The workaround is to install the front-end, stop eucalyptus services, configure the networking manually, bring up eucalyptus services, install UEC node. This process could be better integrated/partially automated if the user could inform the system as to the roles of each network device at front-end installation time.
I think we can assume that by definition the network interface configured in netcfg is public-facing; it's used to do things like 'apt-get update', after all. If there are multiple network interfaces, we can ask later on which one should be used to communicate with nodes.
We don't tell avahi-publish to broadcast on any particular interface, so we probably just need to make sure that the interface is up.
Can we assume DHCP on the private interface for now, if it is distinct from the public one?