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With my current design I have a DL380 Gen9 running ESXi. It has redundant NICs cabled to two different switches. Those switches in turn are both cabled to a third switch that allows my workstation to be connected. My testing so far has shown the following.

Redundant networking diagram

  • If cable C is unplugged, host is still available.
  • If cable D is unplugged, host is still available.
  • if either one of the M4100-50Gs is powered off, host is still available.
  • if cable A is unplugged, host is no longer available.
  • cable B hasn't been tested.

Is there any way with the current hardware that failing cable A could still leave the DL380 accessible to the workstation?

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  • First of all you should connect the two core switches (NetGear M4100...) than unplugging cable A or B won't matter. Don't know if it's viable in your scenario but you should have 2 nics on workstation and redound the access layer (switch NetGear GS748Tv5) so the client has 2 path to the server. if isn't possible to redound the access layer your setup seems decent to me. – eldblz Aug 31 '15 at 20:52
  • @eldblz: Firstly, you don't provide redundant servers and services by using redundant network cards in your client machines. Secondly, what does redound mean? – joeqwerty Aug 31 '15 at 20:54
  • @joeqwerty why not? two nics on the same network segment on different switchs are perfectly fine if you use network teaming: redound is the verb for redundancy no? Should mean "Duplicate" but for redundancy purposes. – eldblz Aug 31 '15 at 20:57
  • So scale that out to 50 or 500 clients that need to access services provided by the virtual machines on that host. That's not how you do redundancy and high availability. Show me a single example of an enterprise using multiple network cards in their client machines to provide highly available and redundant access to services. – joeqwerty Aug 31 '15 at 20:59
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    If all switches being used support STP You should be able to lose either cable A or B and still function. There just might be a temporary loss in traffic being passed while STP is being recalculated (depending on how you have it configured). – Gene Aug 31 '15 at 21:03
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Assuming there isn't a firewall or router between the end users and the server you could employ STP (spanning tree protocol) and the following layout:

proposed network layout

This would give you the redundancy you are seeking. If a single "core switch" (the m4100-50) goes offline traffic should be able to keep flowing.

Depending on how STP is configured (what type of STP and specific configuration options) and how many switches are involved there is some time required for STP to recalculate, but at this point you're looking at recovery times less than a minute, possibly even just a few seconds.

Additionally, note the inclusion of a link between the "core switches" (the m4100s). If these switches are connected you could lose the left links (2) between the core and edge switches and the B link between the VM host and core switches and still have connectivity.

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  • thank you. It looks like STP is the missing link. I think next I'll read up on Netgear's implementation. – Digital ink Aug 31 '15 at 21:47
  • It was a few years ago, but at the time Netgear's implementations of all spanning tree variants was buggy as hell. We ended up paying a bit more and bought Dell PowerConnects in our access layer instead. HPs are also in the "quality but not ludicrously priced" category. Basically, anything but Cisco is generally fine for the access layer. – rmalayter Aug 31 '15 at 23:23
  • @rmalayter, were you running all Netgear hardware, or were you mixing and matching? I'd imagine that STP using only Netgear switches should work fine. – Gene Sep 1 '15 at 13:46
  • @Donovan, rmalayter brings up a good point. The usefulness and stability of STP may vary between vendors, and for "prosumer" hardware it might not be all that great. Make sure you do plenty of testing. If you end up looking into different hardware I also recommend looking at HP ProCurve equipment. They make good stuff. – Gene Sep 1 '15 at 13:47
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    For the level of operation we have the Netgear switches have done fine. I've never asked much of them. Just simple switching and light VLANing. I guess I could say the worst thing about the network is its all Netgear but then the best thing about it is that... Its all Netgear. Heh. I don't have any formal networking training so I suppose there will be lots of testing in my future. Thanks everyone. – Digital ink Sep 2 '15 at 16:59

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