Red Hat / CentOS Linux: Explain Use of Network Interface virbr0

Q. I've installed Red Hat Enterprise Linux 5.2 and I see virbr0 network interface along with my eth0 interface? What it is? How do I disable or remove virbr0?

A. virbr0 is xen interface used by Virtualization guest and host oses for network communication. Following are the packages under Red Hat / CentOS Linux:
Group: Virtualization
Description: Virtualization Support.
Mandatory Packages:
=> xen
=> kernel-xen
Default Packages:
=> virt-manager
=> Virtualization-en-US
=> gnome-applet-vm
=> libvirt
You can disable virbr0 if you don't need xen Virtualization support, enter:
# yum groupremove "Virtualization"
Sample output:

Loading "rhnplugin" plugin
Loading "security" plugin
Setting up Group Process
rhel-x86_64-server-vt-5   100% |=========================| 1.4 kB    00:00
rhn-tools-rhel-x86_64-ser 100% |=========================| 1.2 kB    00:00
rhel-x86_64-server-5      100% |=========================| 1.4 kB    00:00
No package matched to remove
No package matched to remove
No package matched to remove
No package matched to remove
No package matched to remove
Resolving Dependencies
--> Running transaction check
---> Package libvirt.x86_64 0:0.3.3-7.el5 set to be erased
--> Processing Dependency: libvirt.so.0()(64bit) for package: libvirt-python
--> Processing Dependency: libvirt = 0.3.3 for package: libvirt-python
--> Running transaction check
---> Package libvirt-python.x86_64 0:0.3.3-7.el5 set to be erased
--> Processing Dependency: libvirt-python for package: rhn-virtualization-host
--> Running transaction check
---> Package rhn-virtualization-host.noarch 0:1.0.1-55 set to be erased
--> Finished Dependency Resolution
Dependencies Resolved
=============================================================================
 Package                 Arch       Version          Repository        Size
=============================================================================
Removing:
 libvirt                 x86_64     0.3.3-7.el5      installed         3.4 M
Removing for dependencies:
 libvirt-python          x86_64     0.3.3-7.el5      installed         230 k
 rhn-virtualization-host  noarch     1.0.1-55         installed         155 k
Transaction Summary
=============================================================================
Install      0 Package(s)
Update       0 Package(s)
Remove       3 Package(s)
Is this ok [y/N]: y
Downloading Packages:
Running rpm_check_debug
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
  Erasing   : libvirt-python               ######################### [1/3]
  Erasing   : rhn-virtualization-host      ######################### [2/3]
Stopping crond: [  OK  ]
Starting crond: [  OK  ]
  Erasing   : libvirt                      ######################### [3/3]
Removed: libvirt.x86_64 0:0.3.3-7.el5
Dependency Removed: libvirt-python.x86_64 0:0.3.3-7.el5 rhn-virtualization-host.noarch 0:1.0.1-55
Complete!