Category: Virtualization

Chris sent me an interesting question:

Imagine L2 traffic between two VMs on different ESX hosts, both using Nexus 1000V. Will the physical switches see the traffic with source and destination MACs matching the VM’s vNICs or traffic on NX1000V “packet” VLAN between VEMs (in this case, the packet VLAN would act as a virtual backplane)?

It seems that most networking vendors consider the Flat Earth architectures the new bonanza. Everyone is running to join the gold rush, from Cisco’s FabricPath and Brocade’s VCS to HP’s IRF and Juniper’s upcoming QFabric. As always, the standardization bodies are following the industry with a large buffet of standards to choose from: TRILL, 802.1ag (SPB), 802.1Qbg (EVB) and 802.1bh (Port extenders).

The following design challenge landed in my Inbox not too long ago:

My organization is the in the process of building a completely new data center from the ground up (new hardware, software, protocols ...). We will currently start with one site but may move to two for DR purposes. What DC technologies should we be looking at implementing to build a stable infrastructure that will scale and support technologies you feel will play a big role in the future?

In an ideal world, my answer would begin with “Start with the applications.”

I was sort of upset that my vacations were making me miss the VMware vSphere 5.0 launch event (on the other hand, being limited to half hour Internet access served with early morning cappuccino is not necessarily a bad thing), but after I managed to get home, I realized I hadn’t really missed much. Let me rephrase that – VMware launched a major release of vSphere and the networking features are barely worth mentioning (or maybe they’ll launch them when the vTax brouhaha subsides).

Chris Marget sent me the following interesting observation:

One of the things we learned back at the beginning of Ethernet is no longer true: hardware filtering of incoming Ethernet frames by the NICs in Ethernet hosts is gone. VMware runs its NICs in promiscuous mode. The fact that this Networking 101 level detail is no longer true kind of blows my mind.

So what exactly is going on and does it matter?

You probably know the old saying – if the mountain doesn’t want to come to you, you have to go out there and climb it. vCider, a brand-new startup launching their product at Gigaom Structure Launchpad, decided to do something similar in the server virtualization (Infrastructure-as-a-Service; IaaS) space – its software allows IaaS customers to build their own virtual layer-2 networks (let’s call then vSubnets) on top of IaaS provider’s IP infrastructure; you can even build a vSubnets between VMs running within your enterprise network (private cloud in the cloudy lingo) and those running within Amazon EC2 or Rackspace.

Full disclosure: Chris Marino from vCider got in touch with me in early June. I found the idea interesting, he helped me understand their product (even offered a test run, but I chose to trust the technical information available on their web site and passed to me in e-mails and phone calls), and I decided to write about it. That’s it.

One of the implications of Virtual Machine (VM) mobility (as implemented by VMware’s vMotion or Microsoft’s Live Migration) is the need to have the same VLAN configured on the access ports connected to the source and the target hypervisor hosts. EVB (802.1Qbg) provides a perfect solution, but it’s questionable when it will leave the dreamland domain. In the meantime, most environments have to deploy stretched VLANs ... or you might be able to use hypervisor-aware features of your edge switches, for example VM Tracer implemented in Arista EOS.

Two vSwitch portgroup-related questions:

• Can you configure the same VLAN on two portgroups in the same vSwitch? How about vDS?
• Can VMs attached to two different portgroups in the same ESX host talk to each other directly or do they have to go communicate through an external switch (or L3 device)?

Got your answers? Now click the Read more ... link.

A few years ago Cisco introduced an interesting concept to the data center networking: fabric extenders, devices acting like remote linecards of a central switch (Juniper’s “revolutionary” QFabric looks very similar from a distance; the only major difference seems to be local switching in the QF/Nodes). Cisco’s proprietary technology used in its FEX products became the basis for 802.1Qbh, an IEEE draft that is supposed to standardize the port extender architecture.

If you’re not familiar with the FEX products, read my “Port or Fabric Extenders?” article before continuing ... and disregard most of what it says about 802.1Qbh.

The Edge Virtual Bridging (EVB; 802.1Qbg) standard solves two important layer-2-based virtualization issues:

• Automatic provisioning of access switches based on hypervisor-signaled information (discussed in the EVB eases VLAN configuration pains article)
• Multiplexing of multiple logical 802.1Q links over a single physical link.

Logical link multiplexing might seem a solution in search of a problem until you discover that VMware-related design documents usually recommend using 6 to 10 NICs per server – an approach that either wastes switch ports or is hard to implement with blade servers’ mezzanine cards (due to limited number of backplane connections).