Category: virtualization

Almost exactly two years ago I wrote an article describing the benefits and drawbacks of virtual appliances, where I listed virtualization overhead as one of the major sore spots (still partially true). I also wrote: “Implementing routers, switches or firewalls in a virtual appliance would just burn the CPU cycles that could be better used elsewhere.” It’s time to revisit this claim.

VXLAN, one of the first MAC-over-IP (overlay) virtual networking solutions is definitely a major improvement over traditional VLAN-based virtual networking technologies … but not without its own scalability limitations.

When I wrote the Virtual switches need BPDU guard blog post, I speculated that you could shut down a whole HA cluster with a single BPDU-generating VM ... and got a nice confirmation during the Troopers 13 conference – ERNW specialists successfully demonstrated the attack while testing the security aspects of a public cloud implementation for a major service provider.

For more information, read their blog post (they also have a nice presentation explaining how a VM can read ESXi hard drive with properly constructed VMDK file).

Most application stacks built today rely on decades-old security paradigm: individual components of the stack (web servers, app servers, database servers, authentication servers ...) are placed in different security zones implemented with separate physical devices, VLANs or some other virtual networking mechanism of your choice.

The security zones are then connected with one or more firewalls (when I was young we used routers with packet filters), resulting in a crunchy edge with squishy core architecture.

Are you old enough to remember the days when operating systems had no file system? Fortunately I never had to deal with storing files on one of those (I was using punch cards), but miraculously you can still find the JCL DLBL/EXTENT documentation online.

On the other hand, you probably remember the days when a SCSI LUN actually referred to a physical disk connected to a computer, not an extensible virtual entity created through point-and-click exercise on a storage array.

You might wonder what the ancient history has to do with virtual networking. Don’t worry we’re getting there in a second ;)

Yesterday I wrote that it’s pretty easy to develop a VLAN provisioning application (integrating it with vCenter or System Center earns you bonus points, but even that’s not too hard), so based on the frequent “I hate using CLI to provision VLANs” rants you might wonder where all the startups developing those applications are. Simple answer: there’s no reasonably-sized market. How would I know that? We’ve been there.

I love(d) listening to the Packet Pushers podcast and came to expect the following rant in every SDN-focused episode: “I’m sick and tired of using CLI to manually provision VLANs”. Sure, we’re all in the same boat, but did you ever do something to get rid of that problem?

Another day, another interesting Expert Express engagement, another stretched layer-2 design solving the usual requirement: “We need inter-DC VM mobility.”

The usual question: “And why would you want to vMotion a VM between data centers?” with a refreshing answer: “Oh, no, that would not work for us.”

On January 22nd NEC launched another component of their ProgrammableFlow architecture: a virtual switch for Hyper-V 3.0 environment. The obvious questions to ask would be: (a) why do we care and (b) how’s that different from Nicira or BigSwitch.

TL&DR summary: It depends.

In August 2011, when NVGRE draft appeared mere days after VXLAN was launched, I dismissed it as “more of the same, different encapsulation, vague control plane”. Boy was I wrong … and pleasantly surprised when I figured out one of the major virtualization vendors actually did the right thing.

TL;DR Summary: Hyper-V Network Virtualization is a layer-3 virtual networking solution with centralized (orchestration system based) control plane. Its scaling properties are thus way better than VXLAN’s (or Nicira’s … unless they implemented L3 forwarding since the last time we spoke).

Mark Berly, the guest star of my VXLAN Technical Deep Dive webinar focused on VXLAN gateways. Here’s the first part of his presentation, explaining what VXLAN gateways are and where you’d need them.

In a comment to the Firewalls in a Small Private Cloud blog post I wrote “VXLAN is NOT a viable inter-DC solution” and Jason wasn’t exactly happy with my blanket response. I hope Jason got a detailed answer in the VXLAN Technical Deep Dive webinar, here’s a somewhat shorter explanation.

Kaage added a great comment to my Virtual Firewall Taxonomy post:

And many of physical firewalls can be virtualized. One physical firewall can have multiple virtual firewalls inside. They all have their own routing table, rule base and management interface.

He’s absolutely right, but there’s a huge difference between security contexts (to use the ASA terminology) and firewalls running in VMs.

Based on readers’ comments and recent discussions with fellow packet pushers, it seems the marketing departments and industry press managed to thoroughly muddy the virtualized security waters. Trying to fix that, here’s my attempt at virtual firewall taxonomy.

Mrs. Y, the network security princess, sent me an interesting design challenge:

We’re building a private cloud and I'm pushing for keeping east/west traffic inside the cloud. What are your opinions on the pros/cons of keeping east/west traffic in the cloud vs. letting it exit for security/routing?

Short answer: it depends.