10 Responses

  1. Nick Cutting
    Nick Cutting at |

    While not recommending VLT/LACP down to the hosts, for ESX hosts not using NSX – do you still recommend using VLT up to the spine/core switches? I plan on connecting 2 4820t’s up to a cisco 68k VSS pair, and in Nexus world, we could do a “back-to-back” style VPC – is there something similar available for VLT (I understand the VSS side would just be a single control plane multichassis etherchanel, with 2 ports on each 68k)

    Any thoughts?

  2. Nick Cutting
    Nick Cutting at |

    Thank you, yes I am going to thoroughly test all failure scenarios. Definitely will use the static LAG between the Dell switches. I am a little unsure about the QSFP to 10Gig breakout cables, as to how they will interoperate with the cisco 6880 chassis 10gig ports. one reason being that although not a problem now, inter-rack leaf/spine could be an issue if the 10 gig end is like a twixax calbe rather than a transiever that accepts fiber. The 4x10Gig to QSFP cable for the cisco 6880 is not available until April, and the code required to run it possibly the end of the year, so its 10 gig uplinks for now. As for layer 3 to the leaf – this is not going to fly with the server chaps, at least not this year.

    1. @vcdxnz001
      @vcdxnz001 at |

      Yeah, need to be a bit careful with the break out cables when connecting to Cisco. Cisco really only likes to use their own cables and transceivers, so you may need to issue the command service unsupported-transceiver. Best to speak to your Cisco rep or TAC about that. Across racks, fibre is definitely recommended. twinax is severely limited in terms of distance. I use breakout cables in my lab, but I've got all Dell switches. So it works just fine.

  3. Rob
    Rob at |

    Great Blog. I have been doing some proof of concept work with 2 Dell S4048-ON switches. I am incorporating the VLT domain (similar to you), and now trying to add some hosts into the mix.

    I have a couple of powerful desktop computers with 10G qlogic NICs for testing. I am trying to figure out what I am doing wrong as the example you have posted (configured on both switches), leads to my Port Channel 1 reporting – Port-channel 1 is up, line protocol is down(minimum links not up).

    There are 4 desktops ESX1 – ESX4 respectfully, running v6 with vDS. All ESX hosts has an SFP+ connection to both S1 and S2 via twinax. Since the ESX host is connected to both swtiches, and both switches are a VLT pair, what am I missing?


  4. Luis
    Luis at |

    Hello, awsome blog. We are having the same problem as Rob, we have VLT in 2 Dell S4048-ON but when we create a port-channel with LACP to connect a ESXI host, the port-channel did not work and says protocol down (minium links not up) Do you know what can be wrong?


    1. rob
      rob at |

      I had figured this out shortly after posting. Considering the initial lack of response, I didn’t bother updating my comment.

      Long story short, the virtual distributed switch needs to be completely setup before you can take advantage of the port channel – or at least for it be seen in vmware.

      Obviously I was continually doing something wrong that broke management connection. This is partly due to my mis configuration of tagged vs untagged which was different than what I was used to. So temporarily, I used a single gb connection for all management. When I was confident that everything was good, I created the 10gb lagg and migrated all port groups to use it.

      My Dell servers have a 4 port gb nic and 2 x 10gb qlogic adpters. Everything is working as expected now.

  5. Luis
    Luis at |

    vcdxnz001 and rob, how are you?

    We did a pannic question the other day, but we also solve the problem, and also was part of vmware and the distributed switch configuration. Once it was properly configured, the LACP port-channel goes up correctly in the switches. We have LACP port-channel and vlan tagging properly working.



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