Azure NSG Creation Error - Invalid Address Prefix - PowerShell
Last week I came across an issue when defining a CIDR value for "SourceAddressPrefix" in a PowerShell variable. No matter way I was defining the SourceAddressPrefix variable as, it responded with "Invalid address prefix" when trying to create an Azure Network Security Group rule.
Problem
PowerShell New-AzNetworkSecurityGroup responding with "Invalid address prefix" error.
PowerShell Command (Does not work)
// Define Source Address prefix
$sourceAddressPrefix = @("10.10.10.1/29")
// Define rule
$rule1 = New-AzNetworkSecurityRuleConfig -Name rdp-rule -Description "Allow RDP" -Access Allow -Protocol Tcp -Direction Inbound -Priority 100 -SourceAddressPrefix $sourceAddressPrefix -SourcePortRange * -DestinationAddressPrefix * -DestinationPortRange 3389
// Define Network Security Group to deploy new rule to
$nsg = New-AzNetworkSecurityGroup -ResourceGroupName "cloudaen-test" -Location "eastus" -Name "nsg" -SecurityRules $rule1I was even trying to define $sourceAddressPrefix as:
$sourceAddressPrefix = "10.10.10.1/29"
$sourceAddressPrefix = @("10.10.10.1/29")
[String[]]$sourceAddressPrefix = "10.10.10.1/29"Solution
It was as simple as having proper CIDR notation. If you notice, 10.10.10.1/29 is not proper notation, and it was as simple as replacing it with 10.10.10.0/29
PowerShell Command (Working commands)
// Define Source Address prefix
$sourceAddressPrefix = @("10.10.10.0/29")
// Define rule
$rule1 = New-AzNetworkSecurityRuleConfig -Name rdp-rule -Description "Allow RDP" -Access Allow -Protocol Tcp -Direction Inbound -Priority 100 -SourceAddressPrefix $sourceAddressPrefix -SourcePortRange * -DestinationAddressPrefix * -DestinationPortRange 3389
// Define Network Security Group to deploy new rule to
$nsg = New-AzNetworkSecurityGroup -ResourceGroupName "cloudaen-test" -Location "eastus" -Name "nsg" -SecurityRules $rule1Summary
Sometimes PowerShell does not respond with a detailed message and you tend to overthink the problem. In this case, it was a simple CIDR notation causing the issue with a command.
