Hyper-V Network Fix

Fix-HvNetwork.ps1

<#
.SYNOPSIS
Apply a defined IP network to the Hyper-V Default Switch
.DESCRIPTION
Apply a defined IP network to the Hyper-V Default Switch

After host restart, the Hyper-V Default Switch IP network changes to a non-deterministic value. The Default Switch
provides DHCP and NAT services to allow VM's to communicate to the outside and Internet. The changing IP network
presents challenges for VM's with static IP addresses on the Default Switch.

This script defines a network (in the form of the actual interface IP and prefix length) and will add the network
(as an additional IP address) to the Default Switch's VM-facing interface and restart necessary services.
.NOTES
Removing the current address and replacing it with a new one does not seem to function reliably given Hyper-V internals.
The reliable way to provide static addressing (and still provide NAT for outside access) is by adding an IP address.

Given specific services to be restarted, administrative privileges are required.

At times the restart of the Internet Connection Sharing (ICS/SharedAccess) service fails, but the service does pick up
the configuration changes. ICS is responsible for the NAT services.

Windows 11 22H2 changed "vSwitch (Default Switch)" interface to be hidden by default. Get-NetAdapter now searches hidden
 adapters as well. To find your interface/adapter anme (if different), use Get-NetAdapter -IncludeHidden.
.INPUTS
None
.OUTPUTS
None
.EXAMPLE
#>

[CmdletBinding()]
Param()

$Config = @{}
# Desired IPv4 address assigned to Hyper-V default network interface. Represents the default gateway for the network
$Config.Add('IPv4Address', '172.30.144.1')
# Desired IPv4 netmask for Hyper-V default network. Hyper-V defaults to a 255.255.240.0, a /20
$Config.Add('IPv4PrefixLength', 20)
# Name of the Hyper-V default network interface
$Config.Add('InterfaceAlias', 'vEthernet (Default Switch)')
# Do not set the InterfaceIndex, will be determined at runtime based on the InterfaceAlias
$Config.Add('InterfaceIndex', $null)
# Duration to wait after restarting services
$Config.Add('SleepSeconds', 12)

# Verify running as Administrator (for service restarts) or error and stop
try {
   $WindowsIdentity = [System.Security.Principal.WindowsIdentity]::GetCurrent()
   $WindowsPrincipal = New-Object -TypeName System.Security.Principal.WindowsPrincipal -ArgumentList $WindowsIdentity
   if($WindowsPrincipal.IsInRole([System.Security.Principal.WindowsBuiltInRole]::Administrator)) {
      Write-Information ($MyInvocation.MyCommand.Name + ': ' + $WindowsPrincipal.Identity.Name + ' running as Administrator') -InformationAction Continue
   }
   else {
      throw ($WindowsPrincipal.Identity.Name + ' NOT running as Administrator. Elevate and try again. Stop')
   }
}
catch {
   $Msg = $MyInvocation.MyCommand.Name + ': Error verifying running as Administrator. Stop' + "`n"
   $Msg += $_.Exception.Message
   Write-Error $Msg -ErrorAction Stop
}

# Determine the adapter/interface Index value or error and stop
try {
   $NetAdapter = Get-NetAdapter -IncludeHidden -InterfaceAlias $Config.InterfaceAlias -ErrorAction Stop
   $Config.InterfaceIndex = $NetAdapter.InterfaceIndex
   Write-Information ($MyInvocation.MyCommand.Name + ': Found interface: ' + $Config.InterfaceAlias + '. Index: ' + $Config.InterfaceIndex) -InformationAction Continue
}
catch {
   $Msg = $MyInvocation.MyCommand.Name + ': Failed to locate interface: ' + $Config.InterfaceAlias + '. Stop' + "`n"
   $Msg += $_.Exception.Message
   Write-Error $Msg -ErrorAction Stop
}

# Determine if desired address is assigned
try {
   if(Get-NetIPAddress -InterfaceIndex $Config.InterfaceIndex -IPAddress $Config.IPv4Address -PrefixLength $Config.IPv4PrefixLength -ErrorAction SilentlyContinue) {
      Write-Information ($MyInvocation.MyCommand.Name + ': Found : ' + $Config.IPv4Address + '/' + $Config.IPv4PrefixLength + '. No action required') -InformationAction Continue
      $RestartRequired = $false
   }
   else {
      Write-Information ($MyInvocation.MyCommand.Name + ': Did not find: ' + $Config.IPv4Address + '/' + $Config.IPv4PrefixLength + '. Adding') -InformationAction Continue
      New-NetIPAddress -IPAddress $Config.IPv4Address -PrefixLength $Config.IPv4PrefixLength -AddressFamily IPv4  -InterfaceIndex $Config.InterfaceIndex -ErrorAction Stop | Out-Null
      $RestartRequired = $true
   }
}
catch {
   $Msg = $MyInvocation.MyCommand.Name + ': Failed to add address: ' + $Config.IPv4Address + '/' + $Config.IPv4PrefixLength + '. Stop' + "`n"
   $Msg += $_.Exception.Message
   Write-Error $Msg -ErrorAction Stop
}

# Restart Services - if vmms fails, stop. If ICS fails, not always an indication of failure - don't understand why
if($RestartRequired) {
   try {
      Write-Information ($MyInvocation.MyCommand.Name + ': Restarting Hyper-V Virtual Machine Management Service') -InformationAction Continue
      Restart-Service -Name 'vmms' -ErrorAction Stop
   }
   catch {
      $Msg = $MyInvocation.MyCommand.Name + ': Error restarting Hyper-V Virtual Machine Management Service. Stop' + "`n"
      $Msg += $_.Exception.Message
      Write-Error $Msg -ErrorAction Stop
   }
   Write-Information ($MyInvocation.MyCommand.Name + ': Sleeping for ' + $Config.SleepSeconds + ' seconds') -InformationAction Continue
   Start-Sleep -Seconds $Config.SleepSeconds
   try {
      Write-Information ($MyInvocation.MyCommand.Name + ': Restarting Internet Connection Sharing (ICS) Service') -InformationAction Continue
      Restart-Service -Name 'SharedAccess' -ErrorAction Stop
   }
   catch {
      # Not using Write-Error to stop here given this is frequently NOT an error condition and the end of the script
      Write-Information $_.Exception.Message -InformationAction Continue
      Write-Information ($MyInvocation.MyCommand.Name + ': Error restarting Internet Connection Sharing (ICS) service. Verify VM connectivity anyway as the service frequently picks up the changes') -InformationAction Continue
   }
}

Windows 11 22H2 changed "vSwitch (Default Switch)" interface to be hidden by default. Get-NetAdapter now searches hidden
adapters as well. To find your interface/adapter name (if different), use Get-NetAdapter -IncludeHidden.