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New VMware Fling to improve Network/CPU performance when using Promiscuous Mode for Nested ESXi

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I wrote an article awhile back Why is Promiscuous Mode & Forged Transmits required for Nested ESXi? and the primary motivation behind the article was in regards to an observation a customer made while using Nested ESXi. The customer was performing some networking benchmarks on their physical ESXi hosts which happened to be hosting a couple of Nested ESXi VMs as well as regular VMs. The customer concluded in his blog that running Nested ESXi VMs on their physical ESXi hosts actually reduced overall network throughput.

UPDATE (04/24/17) - Please have a look at the new ESXi Learnswitch which is an enhancement to the existing ESXi dvFilter MAC Learn module.

UPDATE (11/30/16) - A new version of the ESXi MAC Learning dvFilter has just been released to support ESXi 6.5, please download v2 for that ESXi release. If you have ESXi 5.x or 6.0, you will need to use the v1 version of the Fling as it is not backwards compat. You can all the details on the Fling page here.

This initially did not click until I started to think about this a bit more and the implications when enabling Promiscuous Mode which I think is something that not many of us are not aware of. At a very high level, Promiscuous Mode allows for proper networking connectivity for our Nested VMs running on top of a Nested ESXi VMs (For the full details, please refer to the blog article above). So why is this a problem and how does this lead to reduced network performance as well as increased CPU load?

The diagram below will hopefully help explain why. Here, I have a single physical ESXi host that is connected to either a VSS (Virtual Standard Switch) or VDS (vSphere Distributed Switch) and I have a portgroup which has Promiscuous Mode enabled and it contains both Nested ESXi VMs as well as regular VMs. Lets say we have 1000 Network Packets destined for our regular VM (highlighted in blue), one would expect that the red boxes (representing the packets) will be forwarded to our regular VM right?

nested-esxi-prom-new-01
What actually happens is shown in the next diagram below where every Nested ESXi VM as well as other regular VMs within the portgroup that has Promiscuous Mode enabled will receive a copy of those 1000 Network Packets on each of their vNICs even though they were not originally intended for them. This process of performing the shadow copies of the network packets and forwarding them down to the VMs is a very expensive operation. This is why the customer was seeing reduced network performance as well as increased CPU utilization to process all these additional packets that would eventually be discarded by the Nested ESXi VMs.

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This really solidified in my head when I logged into my own home lab system which I run anywhere from 15-20 Nested ESXi VMs at any given time in addition to several dozen regular VMs just like any home/development/test lab would. I launched esxtop and set the refresh cycle to 2seconds and switched to the networking view. At the time I was transferring a couple of ESXi ISO’s for my kicskstart server and realized that ALL my Nested ESXi VMs got a copy of those packets.

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As you can see from the screenshot above, every single one of my Nested ESXi VMs was receiving ALL traffic from the virtual switch, this definitely adds up to a lot of resources being wasted on my physical ESXi host which could be used for running other workloads.

I decided at this point to reach out to engineering to see if there was anything we could do to help reduce this impact. I initially thought about using NIOC but then realized it was primarily designed for managing outbound traffic where as the Promiscuous Mode traffic is all inbound and it would not actually get rid of the traffic. After speaking to a couple of Engineers, it turns out this issue had been seen in our R&D Cloud (Nimbus) which provides IaaS capabilities to the R&D Organization for quickly spinning up both Virtual/Physical instances for development and testing.

Christian Dickmann was my go to guy for Nimbus and it turns out this particular issue has been seen before. Not only has he seen this behavior, he also had a nice solution to fix the problem in the form of an ESXi dvFilter that implemented MAC Learning! As many of you know our VSS/VDS does not implement MAC Learning as we already know which MAC Addresses are assigned to a particular VM.

I got in touch with Christian and was able to validate his solution in my home lab using the latest ESXi 5.5 release. At this point, I knew I had to get this out to the larger VMware Community and started to work with Christian and our VMware Flings team to see how we can get this released as a Fling.

Today, I am excited to announce the ESXi Mac Learning dvFilter Fling which is distributed as an installable VIB for your physical ESXi host and it provides support for ESXi 5.x & ESXi 6.x

esxi-mac-learn-dvfilter-fling-logo
Note: You will need to enable Promiscuous Mode either on the VSS/VDS or specific portgroup/distributed portgroup for this solution to work.

You can download the MAC Learning dvFilter VIB here or you can install directly from the URL shown below:

To install the VIB, run the following ESXCLI command if you have VIB uploaded to your ESXi datastore:

esxcli software vib install -v /vmfs/volumes/<DATASTORE>/vmware-esx-dvfilter-maclearn-0.1-ESX-5.0.vib -f

To install the VIB from the URL directly, run the following ESXCLI command:

esxcli software vib install -v http://download3.vmware.com/software/vmw-tools/esxi-mac-learning-dvfilter/vmware-esx-dvfilter-maclearn-1.0.vib -f

A system reboot is not necessary and you can confirm the dvFilter was successfully installed by running the following command:

/sbin/summarize-dvfilter

You should be able see the new MAC Learning dvFilter listed at the very top of the output.

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For the new dvFilter to work, you will need to add two Advanced Virtual Machine Settings to each of your Nested ESXi VMs and this is on a per vNIC basis, which means you will need to add N-entries if you have N-vNICs on your Nested ESXi VM.

    ethernet#.filter4.name = dvfilter-maclearn
    ethernet#.filter4.onFailure = failOpen

This can be done online without rebooting the Nested ESXi VMs if you leverage the vSphere API. Another way to add this is to shutdown your Nested ESXi VM and use either the “legacy” vSphere C# Client or vSphere Web Client or for those that know how to append and reload the .VMX file as that’s where the configuration file is persisted
on disk.

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I normally provision my Nested ESXi VMs with 4 vNICs, so I have four corresponding entries. To confirm the settings are loaded, we can re-run the summarize-dvfilter command and we should now see our Virtual Machine listed in the output along with each vNIC instance.

nested-esxi-mac-learning-dvfilter-4
Once I started to apply this changed across all my Nested ESXi VMs using a script I had written for setting Advanced VM Settings, I immediately saw the decrease of network traffic on ALL my Nested ESXi VMs. For those of you who wish to automate this configuration change, you can take a look at this blog article which includes both a PowerCLI & vSphere SDK for Perl script that can help.

I highly recommend anyone that uses Nested ESXi to ensure you have this VIB installed on all your ESXi hosts! As a best practice you should also ensure that you isolate your other workloads from your Nested ESXi VMs and this will allow you to limit which portgroups must be enabled with Promiscuous Mode.

VMworld vBrownBag Tech Talk : Nested Virtualization & Dev/Test/Home Lab Panel

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VMworld is only a couple of weeks away and I can not believe this will be my 7th VMworld! My, how time has flown by so quickly. I have been pretty busy these last couple of months finishing up some internal projects as well as starting up a couple of new ones. I had been thinking about submitting a vBrownBag Tech Talk as I have done in past years, but there has just been too much going on. Giving it some more thought, I thought it would be cool to put together a panel of community folks to discuss some of my favorite topics like Nested Virtualization as well as Development/Test and Home Labs.

I am please to announce the VMworld vBrownBag Tech Talk : Nested Virtualization & Dev/Test/Home Lab Panel which will include Sean Crookston, Doug Baer, Nick Marshall and myself as the panelists. I was originally hoping to have a few more folks from the community, but due to the late submission, we ran into scheduling conflicts. I am very excited for this session which will take place on Wednesday, August 27th from 11:45am to 12:15pm (30minutes). I wanted to give a huge shout out to Sean Massey who was originally scheduled to present right after ours but decided to offer us his time slot as 15minutes was going to be tough for a panel discussion. Much appreciated Sean!

Due to the short amount of time, we really want to make the most out of this session and most importantly, make this as interactive as possible with the audience. We would like to collect any questions or topics that folks might be interested and we will pick a couple for the panelists to answer or discuss. We will also have topics that we may raise but it would be much more interesting to hear from you! Please leave a comment if you wish to ask a question and perhaps those that get selected, may even win a prize?

We hope to see you at the Tech Talk and lastly, this is going to be a MUST attend session ... that's all I can really say 🙂

BTW - I also would like to give a shout out to Doug Baer who will be running a VMware Knowledge Expert discussion related to the HOL Lab Environment on Tuesday, August 26 at 1pm PST. Though his focus will primarily be HOL, but as many of you know the underlying technology is Nested Virtualization. A couple of us will also be attending that session, so if there are any questions you would like to ask but did not get a chance to during the Tech Talk, you can also find us there.

How to run Nested Mac OS X guest on ESXi VM on top VMware Fusion?

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You might be asking, why would anyone want to do this? Well, luckily this is not a "because you can" type of answer but was it was an interesting solution that one of our VMware Engineers (Darius) had shared with me after helping out on this VMTN Community forum thread.

The user was running VMware Fusion on his physical Mac OS X system and wanted to be able to test OS X Mavericks under ESXi. Not having a physical ESXi host to test with, the next best thing was to run a ESXi VM under VMware Fusion and then run the Mavericks guest on top of that.

Here is a quick diagram of the user setup:

nested-mac-osx-vm-on-esxi-on-fusion0
The issue with just simply doing this is that for a Mac OS X guest to properly run on ESXi, the underlying hardware must be Apple Hardware. The reason for this is not a technical challenges, but rather a legal one per Apple's EULA. The way in which ESXi detects that the underlying hardware is Apple is by checking whether Apple's SMC (System Management Controller) is available.

In the scenario above, the Nested ESXi VM is not automatically passing through the SMC from the physical Mac OS X system and hence the Mac OS X VM at the very top of the stack will not properly function. The solution that Darius found was to add the following two Advanced VM Settings (VMX) entries to the ESXi VM:

smc.present = "TRUE"
smbios.reflectHost = "TRUE"

This will allow the passing of the underlying SMC up into the Nested ESXi VM which will then allow Mac OS X guest VMs to properly function. We can also confirm this by check the Nested ESXi MOB by pointing a browser to the following URL: https://[ESXI-IP]/mob/?moid=ha-host&doPath=hardware

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If you did not add the two entries above, then the smcPresent property would show up as false. In our case, we did add the following two entries and we now run our Mac OS X Guest. Here are a couple of screenshots of performing this on my iMac at home running the same exact configuration:

nested-mac-osx-vm-on-esxi-on-fusion1nested-mac-osx-vm-on-esxi-on-fusion2
Thanks Darius for sharing this with me and the community! I am sure this will come in handy for anyone wanting to test Mac OS X guests under ESXi but do not have a physical ESXi host and can easily substitute using VMware Fusion.