KVM: Configure libvirt network

List available networks:

% virsh net-list
Name                 State      Autostart
-----------------------------------------
InternalNetwork      active     yes
NattedNetwork        active     yes

Edit the selected network:

% EDITOR="emacs -nw" virsh net-edit InternalNetwork

Add host configuration to XML file:

<network>
  <name>InternalNetwork</name>
  <uuid>aaaabbbb-cccc-dddd-eeee-ffff00001111</uuid>
  <bridge name='virbr1' stp='on' delay='0' />
  <mac address='52:54:00:00:11:22'/>
  <ip address='10.50.1.1' netmask='255.255.255.0'>
    <dhcp>
      <range start='10.50.1.10' end='10.50.1.254' />

      <host mac="52:54:00:20:00:00" ip="10.50.2.10"  name="vm-0.local" />
      <host mac="52:54:00:20:00:01" ip="10.50.2.11"  name="vm-1.local" />
      <host mac="52:54:00:20:00:02" ip="10.50.2.12"  name="vm-2.local" />
      <host mac="52:54:00:20:00:03" ip="10.50.2.13"  name="vm-3.local" />
      <host mac="52:54:00:20:00:04" ip="10.50.2.14"  name="vm-4.local" />

    </dhcp>
  </ip>
</network>

Restart network for changes to take effect:

virsh net-destroy  InternalNetwork
virsh net-start InternalNetwork

Note

If you run net-edit again before restarting network, you’ll see the old configuration as it was before changes..

Troubleshooting: changes not taking effect

I tried this on Debian wheezy 7.4, libvirt 0.9.12.3-1 and changes seem not to have effect.

Launching net-edit a second time shows the unchanged file as it was before the changes.

Further investigation revealed that there are in fact two places in which network configuration is stored:

• /var/lib/libvirt/network/mynetwork.xml This is the actual configuration file used by libvirt to configure dnsmasq
• /etc/libvirt/qemu/networks/mynetwork.xml This is the file in which net-edit writes configuration

Workaround:

Just symlink the folders:

rm -rf /etc/libvirt/qemu/networks
ln -s /var/lib/libvirt/network /etc/libvirt/qemu/networks

Now everything should work fine.

Warning

You cannot symlink just the files, as they get both overwritten each time configuration is saved by net-edit..

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