Mac address spoofing hyper-v 2012

Your application inside your virtual machine wants to send some data to another computer. That goes something like this:. Whatever happens down there just happens. Because this particular Ethernet frame is coming out of a Hyper-V virtual machine, the first thing that it encounters is the Hyper-V virtual switch.

Set static MAC address using Hyper-V Manager

In our scenario, the Hyper-V virtual switch rests atop a team of network adapters. The algorithm decides if load balancing can be applied. It only knows about two or more Ethernet endpoints connected in standard access mode. Allowing that would cause all sorts of problems. For traffic going out anything other than the primary adapter, it uses the MAC address of the physical adapter.

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So, no matter how many physical adapters the team owns, one of two things will happen for each outbound frame:. Note : The visualization does not cover all scenarios.

A virtual network adapter might be affinitized to the second physical adapter. So, our frame arrives at the load balancer. The load balancer has a really crummy job. It needs to make traffic go faster, not slower. Routers need to unpackage inbound Ethernet frames, look at their IP information, and make decisions on how to transmit them.

That requires compute power and time. If it needs too much time to do all this, then people would prefer to live without the load balancer. So, they come up with all sorts of tricks to make traffic faster. One way to do that is by not doing quite so much work on the Ethernet frame. This is a gross oversimplification, but you get the idea:. The team achieves load balancing by placing each virtual network adapter across its physical members in a round-robin fashion. I like this mode as a solution because it does a good job addressing the issue without making any other changes to your infrastructure.

Static and LACP teaming involve your Windows Server system and the physical switch agreeing on a single logical pathway that consists of multiple physical pathways. All MAC addresses are registered on that logical pathway. Therefore, the Windows Server team has no need of performing any source MAC substitution regardless of the load balancing algorithm that you choose.

It means modifying your physical infrastructure. That said, using a static or LACP team will allow you to continue using the Dynamic load balancing algorithm. The third listed resolution suggests disabling the related feature on your load balancer.

Configuring Windows Server Containers To Use DHCP Instead Of NAT

Also, these two manufacturers enable the feature by default. Do what works best for you. In all of these scenarios, the load balancer performs routing. You might do that for performance reasons; as I said above, routing incurs overhead.

However, this all a known quantity and modern routers are pretty good at what they do. If any router is present between the load balancer and the back-end virtual machines, then the MAC address issue will sort itself out regardless of your load balancing and teaming mode selections. What system did you experience it happening? How did you resolve the situation if you were able? The comment section below awaits. Did you know Microsoft does not back up Office data?


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This post is super helpful. I have been trying to get to the bottom of this for days. I was about to switch my nic teaming to Hyper-V port before seeing this, but the article solidified it and your explanation is perfect. Thanks so much.

Set static MAC address on a Hyper-V Server VM - Dimitris Tonias

It was observed only on a certain type of traffic. We have chosen to disable Auto Last Hop on the F5 as the least painful and the quickest solution for now. Looks it helped. Have seen this ever since Windows Server Hyper-V, but never before in previous versions. So we had a clue it was due to the new teaming. Struggled with it for our webserver farms. But enabling this flag creates an external virtual switch. Instead I edit Install-ContainerHost. One small change will do the trick.

Not far from the top is where the parameters are set as script variables.

How to Work with Hyper-V Virtual Network Adapters

Look for a line that reads:. Say what? I was stumped. I tried it again. I asked for help and by the time I got home, I got a tip from one of the folks in Redmond. Have you figured it out yet? Now everything works. Your email address will not be published.