Call for Networking Topics

I’m getting ready to start a “Virtual Networking 101″ series of blog posts, where I’m going to try to help introduce the ideas and concepts of virtual networking to VM admins that might not be familiar with these concepts. These are not deep dives; rather, I’m aiming to provide enough introductory knowledge that VM admins are who aren’t familiar with this stuff can at least understand what’s going on. However, I’ve been working in this stuff for a little while now, so it’s a bit difficult for me to tell what core/base concepts would really be helpful to others.

In that vein, then, I’m asking for you–the readers–to let me know: what core/base concepts of virtual networking would you find most helpful? I’m initially thinking of topics like OpenFlow or network overlays, but what would you find helpful? What topics do you want to see or would find useful? Speak up in the comments below to let me know your thoughts. Thanks!


  1. Preetam’s avatar

    Things which will help me understand networking concept inside vCloud director. Very confusing and the main reason i find them confusing because i have never worked on network side. More use case I get to know easier it becomes to understand that networking.

  2. IE23188’s avatar

    Scott, this is an awesome idea. If you are truly wanting to provide “101″ material then I would start with Layer 2 technology as this is the basis of the virtual network (vSwitch/dvSwitch). Topics like OpenFlow and overlays would be like trying to explain BGP but not mentioning understanding IP addressing. Start at L2 (ARP, Flooding, VLANs, 802.1q, CoS, Port-Channels, etc.). Ping me for any help as I would love to assist in this effort.

    Twitter: @ie23188

  3. VTwindude’s avatar

    Lookin @ vPLEX, OTV, VXLAN, extend layer2 between 2sites :}
    Move more to layer 2 to eliminate recalculations.

  4. slowe’s avatar

    Preetam, I’m not sure how much will be specific to vCloud Director; I’m trying to keep this reasonably vendor-neutral and focused on broad technology concepts and such. However, I suspect that some of the concepts we discuss will help with VCD stuff as well.

    IE23188, thanks for the suggestions. I think that I’ll have to assume some base level of knowledge in networking, but there’s still some rudimentary concepts I can review.

    VTwindude, so it looks like you’re interested in some L2 extension methods as well as network overlays/encapsulation. Does that sound right?

  5. DiscoPosse (aka Eric Wright)’s avatar

    Hi Scott,

    I think that having some physical-to-virtual comparative info will be helpful. I get lots of questions about how it maps against current physical models. I also agree with what VTwindude is saying that the stretched cluster and L2 extension would be a great topic. Your stretched clustering VMUG preso in Toronto was awesome and would be great to bring lots of people up to speed.

    All in all, anything will be good. Thanks for bringing out the awesome content! I’m prepping some similar ground-up posts to get more people ramped up on those introductory concepts so they can explore more from there.



  6. jdotson’s avatar


    I think L2 extensions, network overlays/encapsulation are great subject matter topics. Are you considering incorporating any “101″ lab type exercises that could be referenced to augment this material?

  7. Pete’s avatar

    Scott, you probably have thought of these ideas already, but just in case you hadn’t…

    I think leveraging analogies to what most of us are familiar with (virtualizing the compute side of things) would be a great start. Introducing to the reader what the traditional barriers are with physical networks might work well as a lead-in to the barriers that virtualizing the network will help with. We all probably recall the first time we saw vMotion in action, and couldn’t believe our eyes. Letting the readers know what paradigm shifting features are brought to the table with virtualizing the network would be great. And maybe throw in a simple/practical example of how a virtualized network may look through a combo physical/logical topology diagram. Have the example(s) represent the masses more than the uber-large enterprise environment.

    Keep up the great work.
    - Pete

  8. Iain’s avatar

    Hi Scott,

    Like Preetam, my team works on a complex environment fronted by vCloud director. I think that VTwintude is right about people needing a thorough understanding of layer 2 but if we assume that understanding then this is what I would like to see:

    – A discussion of the various methods of uplink load-balancing and failover for different virtual switches and how they behave when various items fail. From a “101″ perspective knowing what a failure looks like (even if you can’t fix it) is critical.

    – What a port group is, how it functions on various types of virtual switches, and how a port group differs from a VLAN/PVLAN and what the relationship is.

  9. Josh Sinclair’s avatar

    I have always been curious how the vSwitch handles/avoids collisions in a cluster. I run a View environment with 500 desktops in two 8 host clusters and to minimize parent VMs that we had to manage we just stuck them all in a /25 (although aparently now in 5.2 you can use multiple VLANs). I haven’t noticed any networking performance issues, but I know they all have to hit the wire at some point. So I guess the follow on question would be how big can I make my collision domains within a cluster?

  10. Patrick Kremer’s avatar

    I’ll echo the stretch cluster request, it’s like … advanced 101? Maybe 201?

    Some of the stuff that I see confusing junior admins
    - Spanning tree, why there is no implementation in vSwitches, why it’s OK to use portfast
    - LAG, what it is and whether or not to use it in a VMware environment.
    - DMZ and internal traffic on same physical host, different vSwitch and different pNICs. Is there an acutal risk here or just IT Governance freaking out?
    - Real-world use cases for PVLANs

  11. Umair Hoodbhoy’s avatar

    I’d be more interested in ‘day-in-the-life-of-a-packet’ depictions for simple examples. Include lots of diagrams. Perhaps begin with how/whether OVS can substitute the legacy Linux bridge. For example, what are the moving parts behind having KVM and 2 VMs in Ubuntu before and after OVS. What was difficult for me was moving from physical switches to virtual switches before OVS even got into the picture.

  12. Jason Gass’s avatar

    VLANs, PVANS, link aggregation. VXLAN, DMZs, standard vs VDS and pros\cons. I don’t know if you want to get into subnetting as it is covered in so many places, but so many people still don’t know it.

  13. Ed G’s avatar

    Maybe too rudimentary, but I have a hard time with VLANs and trunking in VMWare. I’d love to see that.

  14. Brent Salisbury’s avatar

    Hi Scott, great topics from the feedback. Thats awesome. I am always interested in how folks are looking to integrate their SDN islands into the native network. Whether exiting the DC, carrier PEs into LERs or just draining into a enterprise campus IGP is still rarely discussed. More dialogue about where flow forwarding meets the traditional network will be a good gate to wider adoption and less fear.

    Looking forward to any of these topics!

  15. John Telford’s avatar

    I would like to see Virtual Networking 101 do a VMware SDN deep dive pulling together the fission of Nicira NVP, OpenFlow, and Open vSwitch with NSX. Then show how this new and improved virtual networking world integrates with contemporary network infrastructures.

  16. Ilja’s avatar

    Please spend some time on the topic if openflow, SDN and overlays are the solution, what is the problem? Especially helpful would be to map the problem per customer deployment type (SMB, Large Corp, Service Provider).

  17. Graham’s avatar

    One thing I’d like to see Scott, and maybe it’s more practical than you’re looking for, is how to safely virtualize your firewall. Not vShield or anything like that, but taking your vendors physical pFirewall with eth0 to eth12, and virtualizing it – how do you safely move traffic through your internal network to get to your vFirewall.

  18. Daniel Schrader’s avatar

    Great topic – and lots of useful comments. A few thoughts –
    - Explanation of VMotion – including limitations (esp at a distance)
    - Advantages/disads of big, flat networks
    - Networking and security in virtual environments


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