Bridged Networking on a KVM Hypervisor Revision as of Monday, 21 December 2015 at 02:30 UTC

We will be adding a bridge vnet0 to interface eth0

 [root@otoscope ~]# brctl show
 bridge name bridge id         STP enabled interfaces
 virbr0      8000.000000000000 yes

Now add this to /etc/sysconfig/network-scripts/ifcfg-vnet0

 DEVICE=vnet0
 TYPE=Bridge
 BOOTPROTO=dhcp
 ONBOOT=yes

Add BRIDGE=vnet0 to /etc/sysconfig/network-scripts/ifcfg-eth0:

 # Intel Corporation 82579LM Gigabit Network Connection
 DEVICE=eth0
 BOOTPROTO=dhcp
 HWADDR=00:25:90:53:A0:43
 ONBOOT=yes
 BRIDGE=vnet0

Restart the network service and add the bridge:

 service network restart
 brctl addif vnet0 eth0

Check:

 [root@otoscope ~]# brctl show
 bridge name bridge id          STP enabled interfaces
 virbr0      8000.000000000000  yes   
 vnet0       8000.00259053a043  no           eth0

Now add STP with:

  brctl stp vnet0 on

Firewall Rules

Make sure that you’ve set up the proper forwarding rules with IPTables.
Don’t use a general free-for-all like this, though:

 iptables -A FORWARD -m state --state NEW -j ACCEPT

References