I know three basic modes:1. Libvirt creates virtual bridge (the "default network") and connects guests to it. dnsmasq on host provides both DHCP and DNS to the guests.2... [by jlehtone]
I have a KVM CentOS host with several CentOS guests. All of the guests are using a bridge for network communication. The guests have been up and operational for several months and work properly. The guests can not communicate directly with the host due to the bridge based network configuration. As I understand this is normal.