Create private networks with libvirt
I assume that you have a running debian wheezy host with libvirt and qemu/kvm
installed. You need two guest VMs for this. The first guest will get the IP
192.168.100.2 and the second will get 192.168.100.100. All following commands
must be run with
sudo or under root.
We create a new network named internal with libvirt and use it with the IP range of 192.168.100.2 - 192.168.100.254 to build our private network.
For the network and the two guest VMs we need MAC addresses. Create three random MACs with: (you must run it three times ;))
MACADDR="52:54:00:$(dd if=/dev/urandom bs=512 count=1 2>/dev/null | md5sum | sed 's/^\(..\)\(..\)\(..\).*$/\1:\2:\3/')"; echo $MACADDR
Copy all three to a text editor for later usage. Label the first internal network and the other tow guest 1 and guest 2 for reference.
Let's create the network. Open a new file:
Paste the following template:
<network> <name>internal</name> <forward mode='nat'/> <bridge name='virbr1' stp='on' delay='0'/> <mac address='YOUR_RANDOM_MAC_ADDRESS_FOR_THE_NETWORK'/> <ip address='192.168.100.1' netmask='255.255.255.0'> <dhcp> <range start='192.168.100.2' end='192.168.122.254'/> <host mac='YOUR_RANDOM_MAC_ADDRESS_FOR_GUEST_1' ip='192.168.100.2'/> <host mac='YOUR_RANDOM_MAC_ADDRESS_FOR_GUEST_2' ip='192.168.100.100'/> </dhcp> </ip> </network>
Now replace the uppercase strings with your created MAC addresses and save the file.
Hint I have called the bridge virbr1 because in most cases you will already have another network (virbr0). If you have multiple networks or bridges please select an unused name. Otherwise you will get an error while creating or starting the network.
Now let us define/load the new network:
virsh net-define /etc/libvirt/qemu/networks/internal.xml
From now on, if you want to edit your new network you must use
virsh net-edit otherwise
all changes will be overwritten (there is a warning if you open the file with a normal editor).
If you want to take a look at the new network:
EDITOR=nano virsh net-edit internal
If you already had a network called internal (or want to stop another) use
virsh net-destroy <NETWORK_NAME>
Let's start the network:
virsh net-start internal
You should now be able to ping the first IP of the created range:
You should see an output like:
PING 192.168.100.1 (192.168.100.1) 56(84) bytes of data. 64 bytes from 192.168.100.1: icmp_seq=1 ttl=64 time=0.065 ms 64 bytes from 192.168.100.1: icmp_seq=2 ttl=64 time=0.049 ms
Stop it with ctrl+c.
If you want to autostart the internal network with boot, run:
virsh net-autostart internal
Let's move on and create NICs for the each guest. We open the config of each VM and add a new interface.
Replace the uppercase strings with a) the name of your first vm to edit and b) the MAC address from above for guest 1 and run it:
virsh attach-interface --domain <NAME_OF_GUEST_1_VM> --type network --source internal --model virtio --mac <YOUR_RANDOM_MAC_ADDRESS_FOR_GUEST_1> --config --live
It should yield Interface attached successfully. Repeat the command by replacing the guest name and the MAC address with the ones for the second vm, guest 2.
You can check out the new NICs with:
virsh domiflist <NAME_OF_GUEST_1_VM> virsh domiflist <NAME_OF_GUEST_2_VM>
It should show something like:
Interface Type Source Model MAC ------------------------------------------------------- - network internal virtio YOUR_CREATED_MAC_ADDRESS
Perfect. Now, if the guests are running please shut them down - and I mean shut the down, don't restart them. Otherwise the network and NIC won't be attached.
virsh shutdown <NAME_OF_GUEST_1_VM> virsh shutdown <NAME_OF_GUEST_2_VM>
Check if they are down and if they are, boot them up again:
virsh list --all virsh start <NAME_OF_GUEST_1_VM> virsh start <NAME_OF_GUEST_2_VM>
Add network to guests
Now we will add the newly created interface to each guest. This means you will have to repeat this step for each guest, replacing the MAC and IP accordingly.
Log into the guest:
virsh console <NAME_OF_GUEST_1_VM>
Check for the NIC:
There should be an empty interface. Note the name of it. If the VM had network access before it should be eth1. If you already have multiple interfaces, I think you know what you are doing ;)
Let's add the choosen static IP to:
nano /etc/network/interfaces [... lo ... eth0 ...] auto eth1 iface eth1 inet static address 192.168.100.2 gateway 192.168.100.1 netmask 255.255.255.0
Save it and close it. Restart the networking afterwards with:
And check if you can ping the outside and your internal network on the host machine:
ping github.com ping 192.168.100.1
If both commands return a successful ping all went well. Return the steps for your second guest now.
Add hosts to live-network
All edits to a network require a full restart of the network and all machines attached to it! You can add/remove new guests to running networks with the following:
virsh net-update <NETWORKNAME> add ip-dhcp-host "<host mac='<MACADRESS>' name='<NAME_OR_FQDN>' ip='<GUEST_IP_IN_DHCP_RANGE>' />" --live --config