How to add bridge interface to eth0 for KVM in CentOS 5

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Well, after installed the KVM on CentOS , you may want to have a bridge networking on some of VMs
that you may have created.

Unfortunately, KVM doesn’t set this up automatically like the vmware who set its own device during vm-config.pl.

Luckily there are a lot of “How To” telling on step to make it happened.

One of the step that I tried is as follows :

1. First , need to install some package from rpmforge repo. (better sort out the yum repository for rpmforge first if you haven’t)

The package is:

yum install tunctl -y
yum install bridge-utils -y

if necessary add the following into the /etc/rc.local

# into /etc/rc.local
chown root:kvm /dev/net/tun
cmod 0660 /dev/net/tun

then edit the network-configuration file to reflect the above ..

then amend the network script to something like the following :

/etc/sysconfig/network-scripts/ifcfg-eth0
# Broadcom Corporation NetXtreme BCM5755M Gigabit Ethernet PCI Express
DEVICE=eth0
HWADDR=AA:BB:CC:DD:11:21
ONBOOT=yes
BRIDGE=br0

then create the following new network config file into the same folder.

cat /etc/sysconfig/network-scripts/ifcfg-br0

Assuming the static IP address previously assigned for this device to work. (eth0)

# Realtek Semiconductor Co., Ltd. RTL-8110SC/8169SC Gigabit Ethernet
DEVICE=br0
TYPE=Bridge
BOOTPROTO=static
BROADCAST=192.168.211.255
#HWADDR=AA:BB:CC:DD:11:21
IPADDR=192.168.211.196
IPV6INIT=yes
IPV6_AUTOCONF=yes
NETMASK=255.255.255.0
NETWORK=192.168.211.0
GATEWAY=192.168.212.1
ONBOOT=yes
DELAY=0
STP=off

Then, to use in KVM. Just edit the hardware-config for the VM.

1. Run “virtual-manager.” as the “privileged user ”

2. select which VM to change. and click “Open”. Probably better to notify user before shutting it down for re-configuration.

3. Get to the hardware tab.
Remove the old-network device there.

4. Then “Add Hardware”. Choose “Network”.

5. then the following will appear.. Choose “Physical network interface”.. eth0(bridge) should appear from the dropdown menu.

6. Done.

Then , maybe need to reboot the VM to get the new hardware detected.
And reconfigure the VMs network setting to suit your new “bridge” network IP setting.

Reference :

1. CentOS KVM How To
2. VLAN Bridge

..and special thanks to .sha for the head up .

p/s : this will be very useful for setting up something that requiring bridge network instead of NAT.
Like the “ADAM.NET Utility” to send “UDP / MODBUS” read/write command via network…

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About Namran Hussin

a soft spoken guy... with exceptional interest in computers and technology. I love to learn new thing and also love to break thing for the sake of learning.. but I do abide to the self-imposed limitation or certain thing such as social thing in life, thing can be done and thing that must be avoided at whatever cost such as drug,illegal tracking, smoke,illicit activity..etc.muahahaha let's share what we had in this short term of the life.! make it worth of the living.~

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