I cannot save external mapping on Azure Network Gateway (VPN) NAT Rule - gets saved as external mapping = internal mapping

Question

I am having issues trying to configure a NAT rule on an Azure Virtual Network Gateway. I'm using the sku VpnGw2

I'm using the azure web portal to configure the resource. I want a static EgressSnat rule that maps an VNET address 10.6.0.64/32 to 20.190.117.64/32.

I enter the Mode: EgressSnat, Internal Mappings: 10.6.0.64/32, External Mappings: 20.190.117.64/32 and press Save.

Going back to the NAT rules screen and both Internal and External Mappings are set to 10.6.0.64/32.

What am I doing wrong?

Screenshot 1:

Screenshot 2:

Answer 1

Hello @Matthew Campbell , welcome to the Microsoft Q&A forum.

I tried setting up a similar NAT rule at my end, and I did not face the issue above and the rule was saved correctly.

The issue here might be due to a transient portal error. Can you try below mentioned steps and see if that helps in resolving the issue?

1. Can you try clearing cache and cookies for your browser and then try adding the NAT Rule? if possible using a different browser can help as well. Please let me know if the issue still persists.
2. Can you try enabling the NAT rule using PowerShell commands? This might help us to pinpoint the actual issue. You can run the below mentioned command to add a NAT rule. You can run this command using Azure Cloud shell. $Gw = Get-AzVirtualNetworkGateway -Name "<your-Gw-name>" -ResourceGroupName "<RG_Name>"
   $Egress = New-AzVirtualNetworkGatewayNatRule -name "<rule_name>" -type "static" -mode "EgressSnat" -InternalMapping @("<IPaddress>") -externalmapping @("IPaddress") -InternalPortRange "<port>" -ExternalPortRange "<port>"
   Set-AzVirtualNetworkGateway -VirtualNetworkGateway $gw -NatRule $Egress

Hope this helps! Please let me know if you have any additional concerns. Thank you!