Validating NSX VTEP connectivity

This post was inspired by recent incident at the customer environment where VMs were experiencing networking issues due to MTU size misconfiguration on the TOR switches.

If you ever worked with NSX-V and Logical Switches you are aware that NSX configures VTEP vmnics with MTU equal to 1600 bytes. This allows to support VxLAN encapsulation.
However, between every two VTEP interfaces is an L2 or L3 networking device that is potentially not configured to support baby Jumbo frames (that's another name for 1600 bytes packets).

There are many posts explaining how to check MTU size and network connectivity between VTEP interfaces. It is a simple ping using esxcli:

esxcli network diag ping --netstack=vxlan --host vmknic_IP --df --size=1572

Now, imagine you have a small transport zones with 10 hosts and each host has 2 VTEP interfaces. 

You will need to run the esxcli command 360 times to validate all combinations of VTEP pairs. 

With 64 hosts the number of required ping tests reaches 16,128.  Well, that's obviously something that requires automation. 

Hopefully, the future versions of NSX will have this validation step as part of NSX Health Check. 

Meanwhile, we can take advantage of Powershell to make our VTEP validation test a bit easier.

I didn't spend much time writing the script and had only my home lab for a test, so it definitely may have some bugs. 

Here is the logic of the script:

• Connects to NSX/vCenter and validates that connection was established successfully
• Builds array of Transport Zones and Hosts
• Builds array of Hosts and their VTEPs
• Iterate through each TZ-Host-VTEP and ping all other VTEPs in the transport zone. This is a full-mesh test. 
• The script uses pings with 2 different sizes – 64 and 1572 bytes. The first allows to check for connectivity issues and the larger packet validates that MTU size is configured correctly along the path between two VTEPs.
• The results are displayed on the screen in real-time
• Two reports are produced for each transport zone:
• Summary - a table with Source Host, Destination Host and the test result
• Detailed - a table that contains Hosts, VTEP names and IP Addresses, test result for different packet sizes and the error message, if any. 

Script has been tested with vSphere 6.5 U1 and NSX 6.3.x

Update (9/11/2017) - the script was updated to work with ESXi 6.0 and 6.5 versions.

The following screenshot provides and example of successful tests:






This is an example of error messages when using packet size 1573




As you can see the script can detect different types of issues.

here is a couple of reports' screenshots

Summary Report

Detailed Report

Here is the script code

Feel free to provide feedback on any bugs you may encounter using this script. 

Updating configuration of NSX Controllers and Edge appliances

If you have been playing with NSX you may have noticed that you cannot edit settings of virtual appliances deployed by NSX, e.g. controllers or Edge appliances. That's how VMware want to ensure the best performance of NSX in your environment.  However, there might be cases when you still need to adjust some NSX appliances' settings.

In my case I needed to be able to change Memory Reservation settings. The thing is that all NSX appliances are deployed with 100% of memory reservation. My home lab grew up to almost 200Gb of RAM, but I still struggle with lack of memory especially when I run few nested deployments, each with its own NSX.

I am a big fan on PowerCLI so I tried to use Set-VMResourceConfiguration command let, but that attempt wasn't successful.

as you can see in the screenshot this method is disabled.

You can check all the methods disabled for VMs using this command

(get-vm VMname).ExtensionData.disabledmethod

As you can see the ReconfigVM_Task is in the list of disabled methods, which prevents any changes to the VM config.

There is a way to enable this method, but it can only be done through vSphere MOB, but I personally find it really confusing and not user friendly. And I had no clue how to automate this process. So, I gave up on this.

Then I thought there should be a way to change NSX appliances config through NSX RestAPI. And actually there is.

Here is how you can change the memory reservation of NSX edges using curl.  Update the values in bold before using.

1. Grab the NSX edge config and save it in XML file

curl -k -u 'username:password' -H "Content-Type: application/xml" -X GET https://nsxFQDN:443/api/4.0/edges/Edge-ID/appliances/highAvailabilityIndex  > XXX.xml

2. Update the memory reservation in xml file.

<memoryReservation>
<limit>-1</limit>
<reservation>YYY</reservation>
</memoryReservation>

3. Update the edge config

curl -k -u 'username:password' -H "Content-Type:application/xml" PUT https://nsxFQDN:443/api/4.0/edges/Edge-ID/appliances/highAvailabilityIndex -d "@XXX.xml"

As you can see you can change some settings of the Edge, but you cannot do the same with controllers. At least I couldn't find anything similar for controllers in NSX RestAPI guide. 

Also, it is not easy to automate.  

Here is an example of how you can use PowerCLI to automate RestAPI calls

And here what you can get from the output

From here you can update anything you need and change the config using similar PowerCLI function.

As you can see it is more time consuming way of doing things. and again, this is not applicable for NSX controllers.

So I thought I should go back to the original idea of enabling ReconfigVM_task method and started searching for instructions when I found out (once again) that William Lam has already done this. In this post he explains how you can disable vMotion for some of the VMs by disabling MigrateVM_task method. But the most amazing part of that post was that he created PowerCLI functions to enable/disable any methods without using vSphere MOB.

From here it was really easy to create the following script which changes the memory reservation on any VMs - whether they are deployed by NSX or not.

The script grabs all VMs with 100% of memory reservations and changes this value to 99%.  You can change this value to whatever you prefer. If ReconfigureVM method is disabled the script will re-enable it first. After the memory reservation is updated the script will change the ReconfigVM method back to disabled.

All you need to do is to update the vCenter name and credentials before you run the script.

Here is the example of the script output

A word of caution - this is not officially supported way of changing the settings of NSX appliances.  It works but it's at your own risk.