Redhat KVM – Network bridge

Redhat just released RHEL 5.4 with KVM & Xen both supported in this release, so i have downloaded CentOS 5.4 and try to play around with KVM.

My hardware:

Dell M710 with 8 cores of  Nehalem , 72G of RAMs

My OS:

CentOS 5.4 with KVM & Xen installed

My test guest:

Windows 7

The sweet thing:

The bad thingssss:

  • Xen & KVM cannot run in the same time, it is either KVM or Xen
  • No paravirtualization in KVM, only FULL Virtialization, Xen jhas both!
  • Need driver for network in paravirtualzied mode for XP,Vista,Win7
  • No network bridge setup!! Xen do this automatically for us! Network bridge allow your guest os to have their own IP without sharing with the host! I will cover this later on.

By the end of this post, you should be able to setup your bridge!

No Paravirtualization!

Paravirtualization is greyed!

Setting up network bridge

Here is what  we need to create a bridge so the guest os is able to get IP from our LAN.

1. goto /etc/sysconfig/network-scripts

2. There is only 1 eth is enabled, so i simply backup my original config by

cp ifcfg-eth0 BAK-ifcfg-eth0

3. Then create a network bridge config called ifcfg-br0

vi ifcfg-br0

paste the config, the IPaddr use the original from eth0(your host original IP), example in this case:



4. Then edit ifcfg-eth0 ,

vi ifcfg-eth0

Clear all content and replace with the line below:


5. restart network service or reboot.

service network restart

You should see the bridge appear in virt-manager, it was previously grey out and no selection!

Shared Device now appear!

Shared Device now appear!

Though my tutorial seems easy, but i spend 2 days to find out a solution. I am totally new in networking bridge 🙂 hope this help!

And now my windows 7 guest OS is online!

Windows 7 guest is Online via Bridge!

Windows 7 guest is Online via Bridge!

Qumranet Paravirtualized Ethernet Adapter

Qumranet Paravirtualized Ethernet Adapter

Update : 11th March 2010

I faced issue bringing up the network recently. There is few minor changes.


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






/etc/sysconfig/network-scripts/ifcfg-eth0 has

TYPE=Bridge #if you are using static


Remove HWADDR if there is any!


  1. To be frank, I couldn’t make it working using your notes, but it worked straight away using upstream docs.

    So why don’t you simply follow the guide from the Red Hat website?

  2. Hi man!

    2 questions:

    1, This method works with RHEL 5.4???

    ’cause i did it and the connection br0 is activated in the virt-manager, but my PC lost the connection =S, is it normal? (i don’t think so)

  3. TingWei

    September 26, 2010 at 5:32 pm

    Hi Bro, i tried this with Redhat 5.2 if not mistaken. it should be resolved in latest RH version. 🙂

  4. TingWei

    September 26, 2010 at 5:32 pm

    Hi Bro,

    i was using 5.2 during that time if not mistaken. it should be fixed in latest redhat.

  5. It works fine for me, i use Oracle Linux 6. Thanks!

  6. TingWei

    May 15, 2012 at 10:36 am

    Thanks, i am glad that it works!

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