topic Re: Running multiple VMs with same MAC in VMware Workstation Pro Discussions

Running multiple VMs with same MAC

BillyVSCS — Tue, 12 Sep 2023 20:40:52 GMT

We are virtualizing two servers from a legacy system. Currently there are two servers with 4 system NICs. Each NIC shares the same MAC address. These NICs are on 4 separate LANs that run on hubs, no switches or routers. The traffic is identical on all 4 LANS by design so that whatever NIC is active its receiving the information with no cutover or downtime in receiving the packets. The packets are filtered at Lvl2 by MAC address. When we set this up in workstation pro the VM software only sends directed packets on one of these LANs. The other 3 show no traffic coming in. If we use Wireshark and open cards in promiscuous mode we can see all the traffic so we know the traffic is still present on the LANs. Something in the VMWare software is blocking those packets between the host and the VM.

How do we correct this issue?

Re: Running multiple VMs with same MAC

Technogeezer — Tue, 12 Sep 2023 21:02:41 GMT

Can you provide details on how you set up the virtual networks in Workstation?

By "4 system NICs" is that 4 NICs on each physical machine, or 2 NICs on both of the machines for a total of 4 NICs?

What exactly do you mean by "whatever NIC is active". Are you activating one network interface at a time on the servers?

Re: Running multiple VMs with same MAC

BillyVSCS — Tue, 12 Sep 2023 21:20:40 GMT

Can you provide details on how you set up the virtual networks in Workstation?

We have bridged each physical NIC to a VMNET and then to a VNIC on the VM.

By "4 system NICs" is that 4 NICs on each physical machine, or 2 NICs on both of the machines for a total of 4 NICs?

4 physical NICs on each server. There is a pair that supports function A and another pair supporting function B. If one NIC in a pair fails it switches to the other. The servers are redundant pairs as well so that if one goes down the other immediately takes over.

What exactly do you mean by "whatever NIC is active". Are you activating one network interface at a time on the servers? All NICs are enabled but in each pair only one is being used by the software. If that were to fail it would start reading packets from the other.

None of these NICs have tcp/ip protocols assigned.

Re: Running multiple VMs with same MAC

Technogeezer — Tue, 12 Sep 2023 21:48:28 GMT

If not TCP/IP, what networking stack is in use here?

And, do you have a common MAC addresse on the physical adapters, and another common MAC address configured for each vNIC in the VMs?

Re: Running multiple VMs with same MAC

BillyVSCS — Tue, 12 Sep 2023 21:53:10 GMT

If not TCP/IP, what networking stack is in use here? We are using an NDIS custom packet protocol that filters on MAC address.

And, do you have a common MAC addresse on the physical adapters, and another common MAC address configured for each vNIC in the VMs?

The host NICs have whatever MAC got assigned when the host was created. The VM NICs have all been set to the same MAC address value.

I am not a network engineer. I am a software engineer trying to figure this out so please forgive me if I am not clear on on the networking terminology.

I also want to say ahead of time thanks for even responding, any help will be appreciated at this point.