Same MAC address in 2 different VLANs

Olivier Nicole olivier.nicole at
Thu Jul 25 06:54:53 UTC 2013

> I think you maybe ok. Ive just looked at my esx config and the esx
> management interfaces use their own generated macs, not the physical
> interfaces ones. All the vms obviously use generated macs as well.
> However I only looked over it at a superficial level.
> Have you considered using a tap or spare phyical interface on your flex box
> and not linking it to the network?

Thank you, that was a brilliant idea: Flex only needs that one
interface, with the specific MAC, exists on the host, it does not
specifically try to use that interface for managing licenses, so a tap
hanging to nowhere is the solution.

Best regards,


> On 19 July 2013 10:29, Olivier Nicole <Olivier.Nicole at> wrote:
>> Hello,
>> Could any one comment about the use of the same MAC address in 2
>> separate VLANs?
>> All my machines are connected to 2 VLANs (one public and one private)
>> with no routing in between the VLANs.
>> I used to run a FLEX license manager to a physical machine. When I
>> virtualized that service, I had to use the MAC address of that physical
>> machine for the virtual machine (FLEX is linked to the MAc address and I
>> coul dnot issue new license as licensed the pproduct is not supported
>> anymore). The virtual NIC that has the old MAC address is connected to
>> the public VLAN.
>> Now I want to reuse the physical machine as a VMware server. Dell nor
>> VMware offer a solution to change the MAC address (like
>> ifconfig em0 link xx:xx:xx:xx:xx:xx would do). So I plan to connect the
>> NIC with the incriminated MAC to the private VLAN.
>> Most (if not all) my servers are FreeBSD. Most will access the virtual
>> machine running FLEX and may access the VMware server also. The servers
>> are not VLAN aware.
>> Will this be an issue?
>> Best regars,
>> Olivier
>> --
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