Creating VM and Storage Logical Networks in oVirt/RHEV

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The performance of your virtualization environment is highly influenced by Network configurations. This makes Networking one of the most important factors of any Virtualized infrastructure. In oVirt/RHEV, there are several layers that make up Networking. The underlying physical networking infrastructure is what provides connectivity between physical hardware and the logical components of the virtualization environment.

For improved performance, Logical networks are created to segregate different types of network traffic onto separate physical networks or VLANs. For example, you can have separate VLANs for Storage, Virtual Machine, and Management networks to isolate traffic. Logical Networks are created in a Data Center with each cluster being assigned one or more Logical Network. A single logical network can be assigned to multiple clusters to provide communication between VMs in different clusters.

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Each logical network should have a unique name, data center it resides on, and type of traffic in Virtualization environment to be carried by the network. If the virtual network has to share access with any other virtual networks on a host physical NIC, the Logical networks require setting a unique VLAN tag (VLAN ID). Additional settings that can be configured on a logical network include Quality of Service (QoS) and bandwidth limiting settings.

Types of Logical Networks in oVirt / RHEV

Segregation of traffic types on different logical networks is of paramount importance in any Virtualized environment. During oVirt / RHEV installation, a default logical network, called ovirtmgmt is created. This network is configured to handle all infrastructure traffic and VM network traffic. Example of infrastructure traffic is management, display and migration network traffic.

It is recommended that you plan and create additional logical networks to segregate traffic. The most ideal segregation model is network traffic based on the type. Logical network configuration occurs at each of the following layers of the oVirt environment.

  • Data Center Layer – Logical networks are defined at the data center level.
  • Cluster Layer – Logical networks defined on the data center layer, and added to clusters be be used at that layer
  • Host Layer – On each hypervisor host in the cluster, the virtual machine logical networks are connected and implemented as a Linux bridge device associated with a physical network interface. Infrastructure networks can be implemented directly with host physical NICs without the use of Linux bridges.
  • Virtual Machine Layer – If the logical network has been configured and is available on hypervisor host, it can be attached to a virtual machine NIC on the that host.

Main network types are:

1. Management Network

This type of network role facilitates VDSM communication between oVirt Manager and oVirt Compute hosts. It is automatically created during oVirt engine deployment and it is named ovirtmgmt. It is the only logical network available post installation and all other networks can be created depending on environment requirements.

2. VM Network

This is connected to virtual network interface cards (vNICs) to carry virtual machine application traffic. On the host machine, a software-defined Linux bridge is created, per logical network. The bridge provides the connectivity between the host’s physical NIC and virtual machine vNICs configured to use that logical network.

3. Storage Network

It provides private access for storage traffic from Storage server to Virtualization hosts. For better performance, multiple storage networks can be created to further segregate file system based (NFS or POSIX) from block based (iSCSI or FCoE) traffic. Storage networks usually have Jumbo Frames configured. Storage networks are not commonly connected to virtual machine vNICs.

Storage networks are configured to isolate storage traffic to separate VLANs or physical NICs for performance tuning and QoS

4. Display Network

The display network role is assigned to a network that carries display traffic (SPICE or VNC) of the Virtual Machine from oVirt Portal to host where the Virtual Machine is running. This type of network is not connected to virtual machine vNICs, it is categorized as Infrastructure network.

5. Migration network

The migration network role is assigned to handle virtual machines migration traffic between oVirt hosts. It is recommended to use dedicated non-routed migration network to ensure there is no management network disconnection to hypervisor hosts during heavy VM migrations.

6. Gluster network

The Gluster network role is assigned to logical networks that carries traffic from Gluster Server to GlusterFS storage clusters. It is commonly used in hyper-converged oVirt/RHEV deployment architectures.

Creating Logical Networks on oVirt / RHEV

With the basics on Logical Networks covered, we can now focus on how they can be created and used on the oVirt/RHEV virtualization environments. The creation of logical networks is done under the Compute menu in the Networks page.

In this guide we’ll create new logical network called glusterfs for carrying traffic from Gluster Servers to GlusterFS storage clusters.

Login in to the oVirt Administration Portal as admin user.

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Create new logical network

While on Administration portal menu, click on Network > Networks > New button to create a new logical network.

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You’re presented with the New Logical Network dialog window.

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Fill in the fields under General tab – Data Center, Name Description and other parameters.

You can uncheck VM network for infrastructure and Storage type traffic. Enable if logical network is used for virtual machine traffic

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If using VLAN, enable tagging and input VLAN ID

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If Jumbo frames are supported in your network, you can set custom number as configured at network level.

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Under Cluster you can check list of Clusters where created network will be available. Example for all clusters.

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Specific cluster

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Configuring Hosts to use Logical Networks

In the previous section, we demonstrated how to create logical networks to separate different types of network traffic. In this section we describe the procedures needed to implement the logical networks on cluster hosts.

By default, created logical networks are automatically attached to all clusters in the data center. For the logical network to be used in the cluster, it should be attached to a physical interface on each cluster host. Once this has been done the logical network state of the network becomes Operational.

Login to the host and check available network intefaces

$ ip link show
1: lo:  mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enp1s0:  mtu 1500 qdisc fq_codel master ovirtmgmt state UP mode DEFAULT group default qlen 1000
    link/ether 52:54:00:36:ad:26 brd ff:ff:ff:ff:ff:ff
3: enp7s0:  mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether 52:54:00:31:60:02 brd ff:ff:ff:ff:ff:ff

From the output, the first interface enp1s0 is already used by ovirtmgmt bridge which is mapped to ovirtmgmt network. In the new creation, we shall use enp7s0 network interface.

Assign logical network to an oVirt host

Navigate to Hosts page, click the name of the host to which the network will be attached. Click the Network Interfaces tab to list the NICs available on the host.

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Open Host Networks setup window by clicking “Setup Host Networks. Drag a logical network listed under “Unassigned Logical Networks” section to a specific interface row on the left.

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After dragging the network is assigned to the chosen interface.

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Click the pencil icon to set network parameters. From the window you can set boot protocolIP addressnetmask, and gateway when using static addressing.

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You can as well make network modifications from the optional tabs for IPv6, QoS, and DNS configurations.

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Setting network role at cluster level

The network created can be assigned a specific role under Clusters > Clustername > Logical Networks > Manage Networks

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Assign the role to the network you’re doing modifications for.

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Confirm your network is operational by testing connectivity between hosts / Virtual Machines and desired destination.

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Conclusion

In this article we’ve been able to create a logical network in oVirt/RHEV virtualization platform. We went further and attached it to a physical network interface on one or more hosts in the cluster. Network configurations were made on the network with static network booting. DHCP can also be used as boot protocol. For infrastructure networks you must do configurations at the cluster level to indicate what type of traffic
the network will carry.

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