I was playing with NSX recently and testing the distributed firewall (DFW) that allows for east-west firewalling, aka micro-segmentation.

All was going well when I disconnected my brain for a second and added a rule “deny all all” (Yes I know…). Following that moment facepalm I obviously lost access to the vCenter so I could not remove my rule. I basically cut the tree branch I was sitting on.


Best practice is to have your vCenter server included in the exclusion list!

Obviously I didn’t. VMware actually has a KB for that issue, 2017 so I must not be the first one: 2079620

The only easy fix at the moment is to delete the configuration of the ditributed firewall via the REST API to regain access to the vCenter. I find this fix a little bit clumsy coming from VMware. I am only running a lab so I don’t really care but I can only imagine the furious sweating if someone pushed that rule in prod… In such case you don’t really want to go digging in the doc and get a REST client running and fiddle with the self-signed certificate settings. Actually I’m glad I did that mistake here!

Feature request to VMware: Implement a roll back mecanism or a warning message please.

So here’s what we’re going to do:

  1. Reset firewall configuration via REST API.
  2. Include vCenter server in the exclusion list.
  3. Restore last firewall configuration.

1: Reset firewall configuration via REST API

You can easily do it with Curl, Chrome or Firefox but I wrote a few lines in powershell to simplify the process even more for those who ended up on this page. It will be as long as a copy/paste.

  • Just Copy and paste the following into Powershell. It will prompt for the IP and credentials of NSX Manager.
$NSXmgrIP = Read-Host "Enter IP or FQDN of NSX Manager"

$creds = Get-Credential -Message "NSX Manager credentials"

$bytes = [System.Text.Encoding]::UTF8.GetBytes("$($Creds.UserName):$($Creds.GetNetworkCredential().password)")

$Base64 = [System.Convert]::ToBase64String($bytes)

$header = @{Authorization= "Basic $Base64"}

$uri = "https://$NSXmgrIP/api/4.0/firewall/globalroot-0/config"

Write-warning "Delete firewall configuration? (y/n)"

$confirm = read-host " "

if ($confirm -eq "y") {
    Invoke-RestMethod -Method Delete -Uri $uri -Headers $header
    write-warning "Log in vCenter > Add vCenter to the exclusion list > restore the latest firewall configuration backup > Publish"

The output should be blank and you should have access to vCenter again.

2: Include vCenter server in the exclusion list.

  • Log in vCenter and browse to “NSX Manager” configuration in the “Exclusion list” tab.

  • Click on the green “+” sign and add your vCenter VM. From now on it will be ignored by the firewall.


3: Restore last firewall configuration.

  • Browse to the firewall section of NSX
  • The firewall rules list will be back to the default one - no worries
  • Click on the “Load saved configuration” button above the list


  • Select the latest config (the one containing your genius rule) and click “Load”


  • A warning message is displayed “This will replace the current configuration. All the unsaved changes made on current configuration will be lost. Yes to continue”. Click “Yes”. The configuration is then loaded but not published.


  • Publish the changes.


All your rules are now back and vCenter won’t be impacted anymore.

Conclusion, don’t be like me and double check every single rule before publishing. Especially in prod !!