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  • 1.  Having a NIC for direct comms between two VMs and another NIC for regular network possible?

    Posted Jun 06, 2022 07:03 PM

    Hello,

    Apologies up front if I say something totally wrong.  I am learning VMWare and have never actually implemented anything as I type this.

    Currently, we have two physical servers with two NICs each.  One NIC on each server is plugged into a network switch for normal network communications.  The other NIC on each server has a crossover cable connected to it where the crossover cable plugs into the corresponding NIC on the second server i.e. there is a NIC on each physical server with a crossover cable running directly between them.  This crossover communication is necessary to keep some stuff off the regular network.

    We are planning on implementing these two physical servers in VMs.  For HA, will have two ESX-i host servers.  Can we implement this setup such the two NIC configuration as described above can still be implemented using VMs while being able to take advantage of the two host servers for vMotion where one VM maybe on one host and the other VM maybe on the second host or the two VMs could suddenly be on the same machine?

    I truly hope the above makes sense.  I hate to confuse someone who is trying to help.

    Thoughts?

    Respectfully,

    Chris Smith



  • 2.  RE: Having a NIC for direct comms between two VMs and another NIC for regular network possible?

    Posted Jun 07, 2022 12:00 AM

    Hi Chris,

    If I've understood correctly what you're after, then yes this would be possible but you would still need the crossover cable between the two ESXi hosts to maintain the requirement for keeping some traffic off the production network. The obvious issue with this is that it doesn't scale if you need to add any additional hosts (but this could be resolved by adding a separate switch).

    The ESXi hosts would need one virtual switch backed by your production network interfaces (assume two interfaces for redundancy), and a second virtual switch backed by the crossover interface. So each host would need at least 3 NIC ports.

    The VM's would have two interfaces connected to the port groups of each virtual switch, one for production traffic and the other for direct crossover traffic. When the VM's are on the same host, the traffic should traverse the backplane of the host and then on separate hosts it should traverse the crossover cable. See attached pic of what it looks like in my head.

    Hopefully that makes sense!

    Cheers, Jon



  • 3.  RE: Having a NIC for direct comms between two VMs and another NIC for regular network possible?

    Posted Jun 07, 2022 05:33 AM

     wrote:

    Hi Chris,

    If I've understood correctly what you're after, then yes this would be possible but you would still need the crossover cable between the two ESXi hosts to maintain the requirement for keeping some traffic off the production network.


    Are crossover cables still a thing? I have the impression that it is no longer for Gigabit controllers. I just had to use a regular Ethernet cable way back in 2012 to connect two laptops with Gigabit Ethernet without a switch.



  • 4.  RE: Having a NIC for direct comms between two VMs and another NIC for regular network possible?

    Posted Jun 07, 2022 06:03 AM

    Yes, pretty sure that's what I've done in the past with gigabit NICs. In this scenario, I've generically referred to the direct connection between the two hosts as a crossover connection but technically this would just be a regular ethernet connection and not a crossover cable ... which I remember having to manually crimp in the 90's 



  • 5.  RE: Having a NIC for direct comms between two VMs and another NIC for regular network possible?

    Posted Jun 07, 2022 06:21 AM

    Yeah, that was back in 1990s and it annoyed me when careless project team-mates will mix the lone crossover Ethernet cable we have after use with the regular ones.

    But I am pretty sure I didn't have to use crossover cable in 2012. I connected a Dell Latitude using a regular CAT5e cable to a 2010 MacBook Pro for a P2V of the XP running on the Latitude to a Fusion VM on the MacBook Pro. Both had Broadcom Gigabit Ethernet.



  • 6.  RE: Having a NIC for direct comms between two VMs and another NIC for regular network possible?

    Posted Jun 07, 2022 07:04 AM

    I remember that pain, it was either needing one and not being able to find one or picking an erroneously placed one when all you wanted was a working ethernet cable - the pain was real!



  • 7.  RE: Having a NIC for direct comms between two VMs and another NIC for regular network possible?

    Posted Jun 07, 2022 02:21 PM

    The second to last and last paragraph pretty much says that crossover cables are not required for Gigabit and faster for practical purposes.
    https://en.wikipedia.org/wiki/Medium-dependent_interface#Auto_MDI-X

    It is interesting that from the references that you can see there are two patents that belongs to HPE for this; although looks like both are expired so probably HPE does not collect any more royalty payments from technology licensing.

    https://www.hp.com/hpinfo/abouthp/iplicensing/automdix.html
    https://patents.google.com/patent/US6175865B1/en
    https://patents.google.com/patent/US6460078B1/en

    It is quite possible people who never ever worked 10/100Mbps Ethernet cards have no idea what a crossover Ethernet cable is.



  • 8.  RE: Having a NIC for direct comms between two VMs and another NIC for regular network possible?

    Posted Jan 27, 2023 01:33 PM

    Thanks for the replies everyone!  I had actually forgotten I posted this here.  Our project implementation on this is a ways out so this is still relevant and required to implement.

    Thanks again.

     

    Chris Smith