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For various reasons I have to run a few (≈6) clones of the same virtual machine at my lab ESXi server at work and unfortunately the MAC address must not be changed between the clones. Changing IP is OK though.

How can I make the different virtual machines simultaneously communicate at least with a computer on the network outside the ESXi server, but preferably also with each other?

LapplandsCohan
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  • From my understanding the theoretical minimal separation of to NICs with the same MAC address is to have a router in between. Based on that I added a solution running another VM as virtual router, but please add other solutions that you know of. Maybe ESXi has a built in virtual router and not only virtual switch that I have missed, or maybe a router in between the NICs is not the minimal required separation. – LapplandsCohan Jan 30 '20 at 22:41
  • The scope of a MAC address is the layer-2 broadcast domain to which the host with that MAC address is connected. The broadcast domain is the hosts that would see a layer-2 broadcast (destination `ff:ff:ff:ff:ff:ff` for 48-bit MAC addresses, or `ff:ff:ff:ff:ff:ff:ff:ff` for 64-bit MAC addresses). MAC addresses must only be unique on a broadcast domain. – Ron Maupin Jan 31 '20 at 18:06

2 Answers2

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You don't want VMs with the same MAC on a single vSwitch port group, that's how they work.

If I had to do this I'd end up creating 7 port groups, one for each VM, then if you have to route between them then just create a router VM with at least 7 vNICs, one on each port group, each with a valid IP - obviously each port group will have to have it's own subnet for the routing to work.

Does that make sense?

Chopper3
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From what I understand the theoretical minimal separation of two NICs with the same MAC address is to have a router in between.

You could solve this by adding another VM with 7 virtual NICs running e.g. OPNsense, pfSense, or Freesco. Six of the NICs would be connected to each own virtual switch with one of the different clones on each switch. The 7th NIC would be connected to a VM network with access to the outside physical network.

LapplandsCohan
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