Show 28 – vCloud Network Overlays, OTV, VEPA and networking appliances

It was planned to have a discussion around L2 Data Centre connection the VMworld in Copenhagen but Scott and I could not meetup. So we recorded this podcast to start talking about some of the issues, technology and solutions. I’m not sure that we have all the technology or knowledge in place, so keep watching for more discussions in the future.

This is the second half of the show and you should probably listen to last weeks show to get the whole story at


Scott Lowe Ivan Pepelnjak @ioshints

Layer 2 Data Centre Interconnect – open discussion

  • The challenges of extending L2 DCI network betweens sites.
  • Outlining the threats of large Layer 2 spaces in terms of network vulnerability.
  • quick review of vMotion traffic and its requirements.
  • Reviewing the impact of fault domains and L2 VLAN space as uncontrollabl
  • It’s all about the application.
  • Latency, latency and the impact on vMotion switchover.
  • Greg’s article on the Traffic Trombone and Ivan’s extensions to it.
  • It’s worth remembering that Network Load Balancers can be more effective than using vMotion is certain use cases.
  • vMotion is not for unplanned outages or DR. More for planned outages or possibly workload balancing.
  • Debating whether we are able to QoS L2 traffic when flowing between data centers thus answering the question about guaranteeing levels of service for multiple hosts in a VLAN.
  • Some humour on Pseudowire over MPLS over GRE over IP. But’s its actually real.
  • Some review on the F5 EtherIP technology and whether it’s relevant to the solution.


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Greg Ferro
Greg Ferro is a Network Engineer/Architect, mostly focussed on Data Centre, Security Infrastructure, and recently Virtualization. He has over 20 years in IT, in wide range of employers working as a freelance consultant including Finance, Service Providers and Online Companies. He is CCIE#6920 and has a few ideas about the world, but not enough to really count. He is a host on the Packet Pushers Podcast, blogger at and on Twitter @etherealmind and Google Plus.
Greg Ferro
Greg Ferro
Greg Ferro
  • Michael McNamara

    I really enjoyed listening in on your conversation. I was surprised that no one mention the use of dedicated point-to-point dark fiber as a Data Center interconnect option assuming that your locations are within 50Km of each other.

    Also, was there an issue with the MP3 audio around 25 minutes and 40 seconds? I noticed several drop-outs over a 2 minute duration.


  • Julio

    Why does everyone say OTV is the easiest way to do L2 interconnect? Was I the only one thinking "slam 1 or 2 metro ethernet circuits between the data centers and lock it down the usual way (prune un-needed VLANs off, broadcast/multicast storm suppression, etc.)".

    If you're worried about wasting bandwidth because of STP blocking ports, aggregate the links together using LACP.

    So OTV protects you a little bit from unicast flooding. Is that all it does?

  • Ken Ratliff

    Good conversation, but as mentioned above, it sounded like the recording for someone (Greg?) screwed up, and it sounded like Scott and Ivan were responding to a question we couldn't hear

  • Mark H

    Speak Your Mind ?!?!?!?! – careful where you solicit.
    Greg – this is show 28 (listen to it again).

    I 'love' the way noone expands the acronym OTV.

    Anyway, this was my journey,
    OTV is a newly born Lebanese generalist TV station
    Occupational Trainee visa
    Odor threshold value

    Would suggest a future podcast to bring these all together … for goodness sake give some closure :)

    In spite of the above I do appreciate the effort you guys put into the mp3's (what the @$#^% does it have to do with pods ?)

  • Dmitri Kalintsev

    Just a small note – the IFG is not 6 ms.

    "The minimum interframe gap is 96 bit times (the time it takes to transmit 96 bits of raw data on the medium), which is 9.6 μs for 10 Mbit/s Ethernet, 960 ns for 100 Mbit/s (fast) Ethernet, 96 ns for 1 Gbit/s (gigabit) Ethernet, and 9.6 ns for 10 Gbit/s (10 gigabit) Ethernet." (yes, from Wikipedia)