OVS (Open vSwitch)

Overview
OVS concepts:

1. A switch contains ports
2. A port may have one or more interfaces (Bonding allows more than one interface per port)
3. Packets are forward by flow (tunnel ID / IPv4-IPv6 src or dst IP / input port / Ethernet frame type / VID / TCP-UDP src or dst port / MAC src or dst / ToS-DSCP / ARP-ND src or dst address)  

Benefits from adding OVS to a KVM:

1. host can access guests from host via IP address
2. you can change network configuration and have no need to reboot host (but you must reboot host if 'service network restart' command is issued)
3. no need to create vlans on host's interface and setting them up (everything is done automatically after 'ovs-vsctl set port port-name trunks=VID1,VID2,...,VIDn' command is issued)