OpenNebula allows for the creation of Virtual Networks by mapping them on top of the physical ones. All Virtual Networks are going to share a default value for the MAC preffix, set in the oned.conf file.

There are two types of Virtual Networks in OpenNebula:

• Fixed, defines a fixed set of IP-MAC pair addresses
• Ranged, defines a class network.

Virtual Networks created by oneadmin can be used by every other user.

A fixed network consists of a set of IP addresses and associated MACs, defined in a text file.

We need four pieces of information to define a fixed VN:

• NAME: Name of the Virtual Network.
• TYPE: Fixed, in this case.
• BRIDGE: Name of the physical bridge in the physical host where the VM should connect its network interface.
• LEASES: Definition of the IP-MAC pairs. If an IP is defined, and there is no associated MAC, OpenNebula will generate it using the following rule: MAC = MAC_PREFFIX:IP. So, for example, from IP 10.0.0.1 and MAC_PREFFIX 00:16, we get 00:16:0a:00:00:01. Defining only a MAC address with no associated IP is not allowed.

For example to create a Fixed Virtual Network, called Public with the set of public IPs to be used by the VMs, just create a file with the following contents:

NAME = "Public"
TYPE = FIXED

#We have to bind this network to ''virbr1'' for Internet Access
BRIDGE = vbr1

LEASES = [IP=130.10.0.1, MAC=50:20:20:20:20:20]
LEASES = [IP=130.10.0.2, MAC=50:20:20:20:20:21]
LEASES = [IP=130.10.0.3]
LEASES = [IP=130.10.0.4]

This type of VNs allows for a definition supported by a base network address and a size. So we need to define:

• NAME: Name of the Virtual Network.
• TYPE: Ranged, in this case.
• BRIDGE: Name of the physical bridge.
• NETWORK_ADDRESS: Base network address to generate IP addresses.
• NETWORK_SIZE: Number of hosts that can be connected using this network. It can be defined either using a number or a network class (B or C).

The following is an example of a Ranged Virtual Network template:

NAME = "Red LAN"
TYPE = RANGED

#Now we'll use the cluster private network (physical)
BRIDGE = vbr0

NETWORK_SIZE    = C
NETWORK_ADDRESS = 192.168.0.0

Default value for the network size can be found in oned.conf.

Once a template for a VN has been defined, the onevnet command can be used to create it.

To create the previous networks put their definitions in two different files, public.net and red.net, respectively. Then, execute:

<xterm> $ onevnet -v create public.net $ onevnet -v create red.net </xterm>

Also, onevnet can be used to query OpenNebula about available VNs: <xterm> $ onevnet list NID USER NAME TYPE BRIDGE #LEASES

 2 oneadmin Public           Fixed   vbr1       0
 3 oneadmin Red LAN         Ranged   vbr0       0

</xterm> with USER the owner of the network and #LEASES the number of IP-MACs assigned to a VM from this network.

To delete a virtual network just use onevnet delete. For example to delete the previous networks:

<xterm> $onevnet delete 2 $onevnet delete 'Red LAN' </xterm>

You can also check the IPs leased in a network with the onevnet show command

Check the onevnet command help or reference guide for more options to list the virtual networks.

A lease from a virtual network can be obtained by simply specifying the virtual network name in the NIC attribute.

For example, to define VM with two network interfaces, one connected to Red LAN and other connected to Public just include in the template:

NIC=[NETWORK="Public"]
NIC=[NETWORK="Red LAN"]

You can also request an specific address just by adding the IP or MAC attributes to NIC:

NIC=[NETWORK="Red LAN", IP=192.168.0.3]

When the VM is submitted, OpenNebula will look for available IPs in the Public and Red LAN virtual networks. If successful, the onevm show command should return information about the machine, including network information. <xterm> $ onevm show 12 VIRTUAL MACHINE 12 INFORMATION ID : 12 NAME : server STATE : PENDING LCM_STATE : LCM_INIT START TIME : 07/15 15:30:53 END TIME : - DEPLOY ID: : -

VIRTUAL MACHINE TEMPLATE NAME=server NIC=[

BRIDGE=vbr1,
IP=130.10.0.1,
MAC=50:20:20:20:20:20,
NETWORK=Public,
VNID=5 ]

NIC=[

BRIDGE=eth0,
IP=192.168.0.1,
MAC=00:03:c0:a8:00:01,
NETWORK=Red LAN,
VNID=4 ]

VMID=12 </xterm>

Note that if OpenNebula is not able to obtain a lease from a network the submission will fail.

Now we can query OpenNebula with onevnet show to find out about given leases and other VN information:

<xterm> $ onevnet list NID USER NAME TYPE BRIDGE #LEASES

 2 onedmin  Red LAN         Ranged   vbr0       1
 3 oneamdin Public           Fixed   vbr1       1

</xterm>

Note that there is one LEASE active in each network

<xterm> $ onevnet show 4 VIRTUAL NETWORK 4 INFORMATION ID: : 4 UID: : 0

VIRTUAL NETWORK TEMPLATE BRIDGE=eth0 NAME=Red LAN NETWORK_ADDRESS=192.168.0.0 NETWORK_SIZE=C TYPE=RANGED

LEASES INFORMATION LEASE=[ IP=192.168.0.1, MAC=00:03:c0:a8:00:01, USED=1, VID=12 ] </xterm>

IP 192.168.0.1 is in use by Virtual Machine 12

Hypervisors can attach a specific MAC address to a virtual network interface, but Virtual Machines need to obtain an IP address. There are a variety of ways to achieve this within OpenNebula:

• Obtain the IP from the MAC address, using the default MAC assignment schema (PREFERRED)

• Use the CONTEXT attribute, check the Contextualization Guide

With OpenNebula you can also derive the IP address from the MAC address using the MAC_PREFFIX:IP rule. In order to achieve this we provide a context script for Debian based systems. This script can be easily adapted for other distributions, check dev.opennebula.org.

To configure the Virtual Machine follow these steps:

These actions are to configure the VM, the commands refer to the VMs root file system

• Copy the script$ONE_LOCATION/share/scripts/vmcontext.sh into the /etc/init.d directory in the VM root file system.

• Execute the script at boot time before starting any network service, usually runlevel 2 should work.

<xterm> $ ln /etc/init.d/vmcontext.sh /etc/rc2.d/S01vmcontext.sh </xterm>

Having done so, whenever the VN boots it will execute this script, which in turn would scan the available network interfaces, extract their MAC addresses, make the MAC to IP conversion and construct a /etc/network/interfaces that will ensure the correct IP assignment to the corresponding interface.