Defining a strategy for using virtual switches in your network

As you plan a strategy to up the number of virtual switches in your network, brush up on distributed and non-distributed virtual switch choices.

What's your virtualized switch strategy for your environment? Server virtualization is obviously here to stay. If you are a networking professional working in the enterprise who hasn't had to deal with an environment that has multiple virtual machines at this point, I'd argue that you should be looking for a new environment. Few environments exist where virtualizing support servers using DNS, LDAP or DHCP doesn't make sense. As virtualized server environments mature, so grows the virtualized networking environment that accompanies them.

For most environments, it's inevitable that the number of physical hosts running virtual machines and their virtual switches grows from one server to two, three or dozens of physical servers, for that matter. If your plan is not well thought out, you could end up with an environment with dozens of basically dumb switches in your data center that don't tie into your network management infrastructure and tools. This can make troubleshooting a nightmare or impossible. What happens when you need to get Cisco Netflow data from one of these mystery devices? To what IP address do you point your tools, and to what ports are the virtual machines connected? What happens if a virtual machine moves from one host to another?

More virtual switches for your network

Managing virtual network switch challenges

Using vSphere distributed switches

Virtual switches integrate the network edge

You can treat this blog as an introduction to virtual switches for us networking guys that don't get involved in x86 server virtualization. We'll take a look at four major hypervisors and their switch options. The four hypervisors are VMware vSphere, Microsoft Hyper-V, Citrix XenServer and Kernel-based Virtual Machine (KVM).

Distributed and non-distributed virtual switches

Virtual switches basically fall into two categories -- distributed and non-distributed. Non-distributed switches are virtual switches that have many-to-one switch-to-server relationships. Distributed switches may have a one-to-many switch-to-server relationship. Non-distributed switches are therefore simpler and have fewer features than distributed switches. Non-distributed switches don't take much thought from a hypervisor management perspective to implement. If you are in an environment where there was no collaboration between the networking team and the server team, there's a pretty good chance you have a bunch of non-distributed switches in your environment. The worse scenario is that you have a bunch of distributed switches with no integration with your physical network. Not all configuration standards may apply to the virtual distributed switches, but they should be considered when creating the baseline configuration.

Non-distributed VMware vSphere vSwitch

The first platform we'll look at is VMware vSphere, since it's the gorrilla in the room, when it comes to virtualization. vSphere's default switch is called a vSwitch. A vSwitch is VMware's non-distributed switch. A physical host can have multiple vSwitches. vSwitches are basic in capability and are similar to physical "dumb switches" that have little management capability.

vSphere has two options for distributed switches. VMware comes with a pretty capable distributed switch that support features like NetFlow and port spanning across multiple hypervisors. vSphere is the only hypervisor that has production support for the Cisco Nexus 1000v, which has all the management capability of most physical switches.

Non-distributed Microsoft Hyper-V switch

Officially, Hyper-V only supports a standard non-distributed switch. The features are similar to VMware's vSwitch. Windows Server 2012 Microsoft, however, has been running a beta of the Nexus 1000v.

Open source KVM/XENServer

Both KVM and XENServer are both Open Source hypervisors and support Open vSwitch. Some of you may be familiar with Open vSwitch as the open source switch software that can be run on commodity hardware. Open vSwitch capability has been expanded to run as a virtual distributed switch.

Open vSwitch gives these open sourced hypervisors the same cross hypervisor connectivity options that VMware's distributed switch gives vSphere. This includes the ability to run one virtual switch across multiple hosts, allowing a VM to move hosts but stay on the same switch port.

Both hypervisors support the traditional non-distributed virtual switch as well. It's interesting to note that XenServer 6.0 defaults to Open vSwitch.

As you set your virtual switch deployment strategy, take time to talk to your x86 virtualization team on the network options.

This was first published in April 2013

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