How to remove/turn off/disable Linux KVM virbr0 NAT Interface

A virtual bridge, can be defined as a device that bridges virtual interfaces. It provides an easy means of networking virtual networking devices such as venet (virtual network) or veth (virtual ethernet).

Typically, a virtual bridge Virbr0, has point to point devices such as venet devices. So whenever traffic is directed from the kernel to one of the guest VMs / virtual containers, if the vbridge is configured with the right IP address and subnet information, it accepts traffic from the kernel. Internally, the bridge then forwards the packet to the correct venet interface as it learns their IPs.

So the typical configuration is:

virbr0 ----------> venet0 -----> eth0 192.168.10.2
|
----- > venet 1 -----> eth0 192.168.10.5

In this case virbr0 could have an IP of 192.168.10.7/24. Hence virbr0 takes all traffic for 192.168.10.0 and sends it to the venets which are typically point-point devices.

To disable Network address translation (NAT) forwarding type the following commands:

virsh net-destroy default
virsh net-undefine default
service libvirt-bin restart
ifconfig