I have a CentOS server running KVM and need to connect a virtual network to the internet. The network must be routed or NATted, it must not be bridged (port security). If possible, I would like to connect the network to an alias of eth0 with a second IP address and leave the first IP for the host, but it might be possible to reverse that. The guests don't provide services that need to be internet-accessible, but do need access out and to the host.
I'm unable to find any instructions on doing this with just KVM's networking facilities. There are a good few mentions of how to attach a single machine, or single ports from multiple machines, but nothing discussing how to attach an entire network and have it handle switching traffic between machines. There are a few articles that suggest used a routed virtual network, but that doesn't seem to act any different from a NATed one in this case.
Open vSwitch has been mentioned a few times, although what little documentation exists seems to discuss running it with a bridge. A few articles say that they're running it in NAT mode, and then go on to set up what appears to be a bridge. Regardless, I'm working on building OVS in an attempt to set that up.