> The biggest single up-front difference for me on CentOS machines was > that KVM hosts default to NAT on a private bridge while Xen hosts > default to straight bridging. Some network tweaks are necessary to get > KVM hosts to live on a straight bridge. Sorry, I forgot to add to this before. If you want to use bridging in KVM you need to set up bridge interfaces on the host (br0 and so on) and assign the main IP address to that interface, instead of to the underlying physical one. One more thing, if you assign a bridge to a VLAN interface, you do not need to add the VLAN on the guest, just treat it as a normal interface and the guest will take care of the tagging for you.