NSX Troubleshooting Scenario 2 – Solution

Welcome to the second installment of a new series of NSX troubleshooting scenarios. This is the second half of scenario two, where I’ll perform some troubleshooting and resolve the problem.

Please see the first half for more detail on the problem symptoms and some scoping.

Getting Started

As mentioned in the first half, the problem is limited to a host called esx-a1. As soon as a guest moves to that host, it has no network connectivity. If we move a guest off of the host, its connectivity is restored.


We have one VM called win-a1 on host esx-a1 for testing purposes at the moment. As expected, the VM can’t be reached.

To begin, let’s have a look at the host from the CLI to figure out what’s going on. We know that the UI is reporting that it’s not prepared and that it doesn’t have any VTEPs created. In reality, we know a VTEP exists but let’s confirm.

To begin, we’ll check to see if any of the VIBs are installed on this host. With NSX 6.3.x, we expect to see two VIBs listed – esx-vsip and esx-vxlan.

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NSX Troubleshooting Scenario 2

I got some overwhelmingly positive feedback after posting the first troubleshooting scenario and solution recently. Thanks to everyone who reached out to me via Twitter with feedback and suggestions! Please keep those suggestions and comments coming.

Today, I’m going to post a similar but more brief scenario. This is something that we see regularly in GSS – issues surrounding host preparation!

NSX Troubleshooting Scenario 2

Let’s begin with the usual vague customer problem description:

“We took a host out of the compute-a cluster to do some hardware maintenance. Now it’s been added back and when VMs move to this host, they have no connectivity! We’re using NSX 6.3.2”

This is a fictional scenario of course, but let’s assume that we’ve started taking a look at the environment and collecting some additional data.

As the customer mentioned, they are running NSX 6.3.2 and have a cluster called compute-a:


The host that was taken out of the cluster for maintenance was esx-a1.lab.local. Similar to the previous scenario, the L3 design is pretty much the same:


The web-a1 VM was migrated to each host, and the customer has confirmed that whenever it goes to host esx-a1, it can’t ping anything. The vMotion operation always completes successfully.

From a console of the web-a1 VM, the following destinations were tested:

  1. Default gateway (DLR at
  2. DNS Server (
  3. Internet Location (
  4. Upstream router (
  5. VM in the same subnet/VXLAN and in compute-a cluster (
  6. VM in the same subnet/VXLAN and in compute-b cluster (

None of the above worked.

As soon as the VM is migrated back to esx-a2.lab.local or esx-a3.lab.local, it can communicate once again.

The web-a1 virtual machine is currently in VXLAN 5001 called the ‘Blue Network’:


Taking a look in the NSX vSphere Client UI, we can see that the NSX manager and controllers appear to be in good shape:


The Host Preparation page shows that host esx-a1 is not prepared for some reason!


There is also a VXLAN error that reads:

“VTEP has not been created successfully on the Host.”

Oddly though, if we look at the vmkernel adapter view of the vSphere Web Client, we can see a VXLAN VTEP that exists!


So is this host prepared or not? Either the UI is wrong or there is a problem. After asking the customer some more questions, we’ve been able to determine the steps they did with esx-a1 to get to this state. Unfortunately, the customer we’re talking to is not the same person who made the changes. That individual is on vacation now and can’t be reached – typical.

  1. Host esx-a1 was put into maintenance mode and evacuated of all VMs.
  2. Host esx-a1 was removed from the cluster.
  3. The host was then powered off.
  4. It took several weeks to get the replacement memory for the host, but eventually it was replaced.
  5. Host esx-a1 was powered back on and looked good from a hardware/vSphere perspective.
  6. Host esx-a1 was added back to the compute-a cluster. No errors were reported when this was done.
  7. The host was taken out of maintenance mode.
  8. After a day or two, DRS migrated some VMs to esx-a1 and that was when we noticed applications becoming inaccessible.
  9. To work around the issue, we migrated VMs that were on esx-a1 to other hosts in the cluster and then put DRS into manual mode to prevent anything else from moving to esx-a1.

The customer believes there may have been other things done during troubleshooting but is unsure.

What’s Next?

In a day or two I’ll post the solution and troubleshooting steps necessary to find the underlying cause of this problem. Have a look through the information provided above and let me know what you would check or what you think the problem may be! I want to hear your suggestions!

**EDIT 12/12/2017: The solution to troubleshooting scenario two is now live!

Not only do we want to figure out how things got into this state in the first place, but also how to fix this problem and get things back into a good state.

What other information would you need to see? What tests would you run? What do you know is NOT the problem based on the information and observations here?

Please feel free to leave a comment below or via Twitter (@vswitchzero).

NSX Troubleshooting Scenario 1 – Solution

Welcome to the second half of ‘NSX Troubleshooting Scenario 1’ . For detail on the problem and some initial scoping, please see the first part of the scenario that I posted a few days ago. In this half, I’ll walk through some of the troubleshooting I did to find the underlying cause of this problem as well as the solution.

Where to Start?

The scoping done in the previous post gives us a lot of useful information, but it’s not always clear where to start. In my experience, it’s helpful to make educated ‘assertions’ based on what I think the issue is – or more often what I think the issue is not.

I’ll begin by translating the scoping observations into statements:

  • It’s clear that basic L2/L3 connectivity is working to some degree. This isn’t a guarantee that there aren’t other problems, but it looks okay at a glance.
  • We know that win-b1 and web-a1 are both on the same VXLAN logical switch. We also know they are in the same subnet, so that eliminates a lot of the routing as a potential problem. The DLR and ESGs should not really be in the picture here at all.
  • The DFW is enabled, but looks to be configured with the default ‘allow’ rules only. It’s unlikely that this is a DFW problem, but we may need to prove this because the symptoms seem to be specific to HTTP.
  • We also know that VMs in the compute-b cluster are having the same types of symptoms accessing internet based web sites. We know that the infrastructure needed to get to the internet – ESGs, physical routers etc– are all accessed via the compute-a cluster.
  • It was also mentioned by the customer that the compute-b cluster was newly added. This may seem like an insignificant detail, but really increases the likelihood of a configuration or preparation problem.

Based on the testing done so far, the issue appears to be impacting a TCP service – port 80 HTTP. ICMP doesn’t seem impacted. We don’t know if other protocols are seeing similar issues.

Before we start health checking various NSX components, let’s do a bit more scoping to see if we can’t narrow this problem down even further. Right off the bat, the two questions I want answered are:

  1. Are we really talking to the device we expect from a L2 perspective?
  2. Is the problem really limited to the HTTP protocol?

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NSX Troubleshooting Scenario 1

Welcome to the first of what I hope to be many NSX troubleshooting posts. As someone who has been working in back-line support for many years, troubleshooting is really the bread and butter of what I do every day. Solving problems in vSphere can be challenging enough, but NSX adds another thick layer of complexity to wrap your head around.

I find that there is a lot of NSX documentation out there but most of it is on to how to configure NSX and how it works – not a whole lot on troubleshooting. What I hope to do in these posts is spark some conversation and share some of the common issues I run across from day to day. Each scenario will hopefully be a two-part post. The first will be an outline of the symptoms and problem statement along with bits of information from the environment. The second will be the solution, including the troubleshooting and investigation I did to get there. I hope to leave a gap of a few days between the problem and solution posts to give people some time to comment, ask questions and provide their thoughts on what the problem could be!

NSX Troubleshooting Scenario 1

As always, let’s start with a somewhat vague customer problem description:

“Help! I’ve deployed a new cluster (compute-b) and for some reason I can’t access internal web sites on the compute-a cluster or at any other internet site.”

Of course, this is really only a small description of what the customer believes the problem to be. One of the key tasks for anyone working in support is to scope the problem and put together an accurate problem statement. But before we begin, let’s have a look at the customer’s environment to better understand how the new compute-b cluster fits into the grand scheme of things.

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Check NSX 6.2.x Compatibility Before Upgrading to 6.3.5!

Unlike previous 6.3.x releases, 6.3.5 has some new upgrade minimum version compatibility requirements. This is not only true from a vSphere perspective, but also for the version of NSX 6.2.x you are running. If you are running an older 6.2.0, 6.2.1 or 6.2.2 release of NSX, you’ll need to upgrade to at least 6.2.4 before taking the big step up to 6.3.5. VMware has just updated the NSX Upgrade Matrix to reflect this requirement:


Screenshot taken from the VMware Interoperability Matrix site.

I expect that VMware will update the 6.3.5 release notes and release a new KB article very shortly. I’ll provide some more detail when that is out. In the meantime, please be sure to heed the version requirements or you will most likely run into problems.

Thankfully there aren’t too many customers still running these old releases of 6.2.x, but if you have already attempted the upgrade and hit problems, you’ll need to roll back. If you took a cold-snapshot of the manager or a clone, you can roll back that way. Otherwise, you’ll need to deploy the original 6.2.x OVA again and restore your FTP backup.

** Edit 11/29/2017: VMware has just updated the NSX 6.3.5 release notes to include mention of the minimum version requirements. The following statement was added:

Important: If you are upgrading NSX 6.2.0, 6.2.1, or 6.2.2 to NSX 6.3.5, you must complete a workaround before starting the upgrade. See VMware Knowledge Base article 000051624 for details.

VMware calls it a “workaround” but it’s basically just upgrading to an interim version before going to 6.3.5. In KB 000051624, VMware recommends going to 6.2.9 as that workflow has been tested. I.e. upgrading from 6.2.0 to 6.2.9, and then to 6.3.5. On a positive note, you only need to upgrade your NSX Manager to 6.2.9, no other components need to be upgraded before proceeding on to 6.3.5.

If you attempt an upgrade from 6.2.2 or older releases, my understanding is that the upgrade will appear to be completed successfully, but your configuration will be missing. VMware calls out the remediation steps of rolling back to the previous version should you run into this issue.

NSX Transport Zone Cluster Removal Issues

Ever remove a cluster from your NSX transport zone only to see it reappear on the list of clusters available for disconnection? Unfortunately, the task likely failed but NSX doesn’t always do a very good job of telling you why in the UI.

I was recently attempting to remove a cluster called compute-b from my transport zone so that I could remove and rebuild the hosts within. Needless to say, I ran into some difficulties and wanted to share my experience.

If you are interested in some more detailed instructions on how to decommission NSX prepared hosts, you can check out my post on Completely Removing NSX. From a high level, the steps I wanted to do were the following:

  1. Disconnect all VMs from logical switches in the cluster to be removed.
  2. Remove the cluster from the transport zone. This will remove all port groups associated with the logical switches (assuming no other clusters are connected to the same distributed switch)
  3. ‘Unconfigure’ VXLAN from the ‘Logical Network Preparation’ tab to remove all VTEPs.
  4. Uninstall the NSX VIBs from the Host Preparation Tab.

To begin, I used the ‘Remove VM’ button from the Logical Switches view in NSX. I removed all four of the VMs attached to the only Logical Switch being used at the moment. I saw a bunch of VM reconfigure tasks complete, and assumed it had completed successfully.

I then went to disconnect compute-b from the transport zone called Primary TZ. After removing the cluster and clicking OK, the dialog closed giving the impression that the task was successful. Oddly though, I didn’t see the tasks related to port group removal that I expected to see.


Sure enough, I went back into the ‘Disconnect Clusters’ dialog and saw the compute-b cluster still in the list. Unfortunately, NSX doesn’t appear to report failures for this particular workflow in the UI.

Having worked in support for many years, I followed my first instinct and checked the NSX Manager vsm.log file for detail on why the operation failed. I received the below failure details:

2017-11-24 18:50:13.016 GMT+00:00 INFO taskScheduler-8 JobWorker:243 - Updating the status for jobinstance-101742 to EXECUTING
2017-11-24 18:50:13.022 GMT+00:00 INFO taskScheduler-8 SchedulerQueueServiceImpl:64 - [TF] Created a new bucket for module default_module and total number of buckets 1
2017-11-24 18:50:13.022 GMT+00:00 INFO taskScheduler-8 SchedulerQueueServiceImpl:80 - The task ShrinkVdnScope-vdnscope-1 (1511549412299) [id:task-102755] is added to the SchedulerQueue
2017-11-24 18:50:13.022 GMT+00:00 INFO pool-10-thread-1 ScheduleSynchronizer:48 - Start executing task: task-102755 and running executor threads 1
2017-11-24 18:50:13.042 GMT+00:00 INFO TaskFrameworkExecutor-3 VdnScopeServiceImpl$2:995 - New VDS (count: 1) is being removed when shrinking scope vdnscope-1. Shrinkingwires.
2017-11-24 18:50:13.061 GMT+00:00 ERROR TaskFrameworkExecutor-3 VirtualWireServiceImpl:1577 - validation failed at delete backing for dvportgroup-815 in the scope: vdnscope-1
2017-11-24 18:50:13.061 GMT+00:00 ERROR TaskFrameworkExecutor-3 VdnScopeServiceImpl$2:1015 - Shrink operation failed on TZ vdnscope-1
2017-11-24 18:50:13.061 GMT+00:00 ERROR TaskFrameworkExecutor-3 Worker:219 - BaseException thrown while executing task instance taskinstance-166334
com.vmware.vshield.vsm.vdn.exceptions.XvsException: core-services:819:Transport zone vdnscope-1 contraction error.
 at com.vmware.vshield.vsm.vdn.service.VirtualWireServiceImpl.validateShrink(VirtualWireServiceImpl.java:1578)
 at com.vmware.vshield.vsm.vdn.service.VdnScopeServiceImpl$2.doTask(VdnScopeServiceImpl.java:1001)
 at com.vmware.vshield.vsm.vdn.service.task.AbstractVdnRunnableTask.run(AbstractVdnRunnableTask.java:80)
 at com.vmware.vshield.vsm.task.service.Worker.runtask(Worker.java:184)
 at com.vmware.vshield.vsm.task.service.Worker.executeAsync(Worker.java:122)
 at com.vmware.vshield.vsm.task.service.Worker.run(Worker.java:99)
 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
 at java.lang.Thread.run(Thread.java:745)
2017-11-24 18:50:13.068 GMT+00:00 INFO TaskFrameworkExecutor-3 JobWorker:243 - Updating the status for jobinstance-101742 to FAILED

There is quite a bit there, but the key takeaways are that the task clearly failed and that the reason was: “validation failed at delete backing for dvportgroup-815 in the scope: vdnscope-1

This doesn’t tell us why exactly, but it seems clear that the operation can’t delete dvportgroup-815 and fails. In my experience, 99% of the time this is because there is still something connected to the portgroup.

Since there were only four VMs in the cluster, and no ESGs or DLRs – I wasn’t sure what could possibly be connected. I even shut down all four disconnected VMs and put all three hosts in maintenance mode just to be sure. None of these actions helped.

I then navigated to the Networking view in vCenter to have a look at the DVS associated with the compute-b cluster. In the ‘Ports’ view, you can get a good idea of what exactly is still connected to the distributed switch. To my surprise a VM called win-b1 was actually still showing as ‘Active’ and ‘Connected’ to the dvPortgroup associated with a Logical Switch!


This dvPort state is clearly wrong – first of all, the VM was powered off so it could not be ‘Link Up’. Secondly I thought I had removed the VM. Or did I?


Although I didn’t see any failures, it doesn’t appear that this VM was removed from the Logical Switch. Maybe I missed it, or perhaps it was a quirk due to the bug outlined in KB 2145889 where DirectPath I/O is enabled on VMs created with the vSphere Web Client. This was the only VM that had this option checked off, but despite my best efforts I could not reproduce the problem. Regardless, knowing what the problem was, I could simply disconnect the NIC and add it to another temporary portgroup.

This adjustment appeared to refresh the DVS port state and then I was able to remove the cluster from the Transport Zone successfully. 

When in doubt, don’t hesitate to dig into the NSX Manager logging. If the UI doesn’t tell you why something didn’t work or is light on details, the logging can often set you in the right direction!

NSX 6.3.5 Now Available!

Late yesterday, VMware made available NSX 6.3.5 (Build Number 7119875) for download. This is a full maintenance release including over 32 documented bug fixes. As you may recall, 6.3.4 was a minor patch release with only a few fixes, which is why 6.3.5 has been released so soon afterward.

There are numerous fixes in this release that will be of interest to a lot of customers. Of special note are the fixes related to Guest Introspection – a feature leveraged by 3rd party AV and security products, as well as the IDFW. I was very happy to see that GI got front and center attention in 6.3.5. Along with some needed CPU utilization fixes, there is also a fix for issue number 1897878, outlined in VMware KB 2151235 that I’ve seen quite a bit of in the wild.

Another interesting behavior change is also quoted in the ‘What’s New in 6.3.5’ section:

“Guest Introspection service VM will now ignore network events sent by guest VMs unless Identify Firewall or Endpoint Monitoring is enabled”

This is a feature that we’ve sometimes manually disabled in older releases in very large deployments to improve 3rd party A/V scalability. The vast majority of customers don’t use ‘Network Introspection’ services, so it’s good to see that it’s now off by default unless needed.

Those using Guest Introspection should definitely consider upgrading to 6.3.5.

Another interesting statement that I’m sure many people are interested in is:

“Host prep now has troubleshooting enhancements, including additional information for “not ready” errors”

EAM generally hasn’t provided very descriptive statements in the ‘Not Ready’ dialogue, so this is also a very welcome change.

And of course, the controller disconnect issue and password expiry issues are also fixed in 6.3.5. This obviously brings up a good question – should you still patch with the re-released versions of 6.3.3/6.3.4, or go straight to 6.3.5? I see no reason why you would not go straight to 6.3.5.

Here is some of the relevant information:

NSX 6.3.5 Download Page
NSX 6.3.5 Release Notes

Definitely have a read through the release notes – there are some real gems in there. I hope to get this deployed in my home lab sometime in the next few days!