Libvirt Network Configuration

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Since I want to use bridge network in libvirt, while the standard bridge networking is not available for me to use, so following tips is for creating and managing the networking.

Enable Bridge

In host machine(OpenSuse), create bridge via:

$ sudo brctl addbr br0
$ sudo brctl addif br0 eth0 

This will add eth0 to bridge 0, while in startup file of OpenSuse we will do following:

# pwd
/etc/sysconfig/network
# cat ifcfg-eth0 
BOOTPROTO='static'
STARTMODE='ifplugd'
IFPLUGD_PRIORITY='1'
NAME='RTL8111/8168B PCI Express Gigabit Ethernet controller'
USERCONTROL='no' 
# cat ifcfg-br0 
BOOTPROTO='static'
STARTMODE='auto'
IPADDR='192.168.0.xxx/24'
NAME='Bridge For Virtualization'
BRIDGE='yes'
BRIDGE_PORTS='eth0'
BRIDGE_FORWARDDELAY='0'

So next time reboot you will see br0 hold the address of 192.168.0.xxx, this is the bridge port we have.

Virtual Machine Configuration

First list all of the virtual machine we have

$ sudo virsh list --all
 Id    Name                           State
----------------------------------------------------
 2     Ubuntu12043                    running
 -     OpenContrail                   shut off

Edit the one we want to edit via:

$ sudo virsh edit Ubuntu12043
    <interface type='bridge'>
      <mac address='24:42:53:21:52:49'/>
      <source bridge='br0'/>
      <model type='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
    </interface>

So next time when you boot-up the machine, it will have the physical network which connecting to br0.

Configure route

In virtual machine, give the fixed ip address via:

$ sudo ifconfig eth0 192.168.188.188
$ sudo ip route add 192.168.0.0/24 dev eth0
$ sudo route add default gw 192.168.0.xxx
$ sudo route -n
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface                                                                 
0.0.0.0         192.168.0.119   0.0.0.0         UG    0      0        0 eth0                                                                  
192.168.0.0     0.0.0.0         255.255.255.0   U     0      0        0 eth0                                                                  
192.168.188.0   0.0.0.0         255.255.255.0   U     0      0        0 eth0   

We want make it permanent via:
First make the permanent ip address:

# cat /etc/network/interfaces 
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet static
        address 192.168.188.188
        netmask 255.255.255.0

Second we want to configure the route:

$ tail  /etc/rc.local
ip route add 192.168.0.0/24 dev eth0
route add default gw 192.168.0.xxx
echo "nameserver 114.114.114.114">>/etc/resolv.conf

This will set the route and the default gateway of your device, also the nameserver will be set.
But while in the host machine, you will add following iptables rules:

# ip route add 192.168.188.0/24 dev br0
# iptables -t nat -A POSTROUTING -s 192.168.188.0/24 -j SNAT --to 192.168.0.xxx
# iptables -A FORWARD -s 192.168.188.188 -j ACCEPT

The iptables rules should be saved via iptables-save, while the route rules should be added into following file:

$  cat /etc/rc.d/after.local 
ip route add 192.168.188.0/24 dev br0                

Now reboot the host machine, you route configuration will be saved.