Update the subnet mask for an existing DHCP scope

Set-DHCPv4SubnetMask.ps1

$ServerName = "CORP-DHCP01"
$ScopeId = "10.10.10.0"
$SubnetMask = "255.255.255.0" #This is the NEW mask that will be applied
$ServerFile = "c:\temp\dhcp_backup.xml"
$ServerFileBackup = "c:\temp\dhcp_backup2.xml"
$ScopeFile = "c:\temp\scope_$ScopeId.xml"
 
#backup entire server, just in case
Export-DhcpServer -ComputerName $ServerName -Leases -File $ServerFile
 
 
Export-DhcpServer -ComputerName $ServerName -ScopeId $ScopeId -Leases -File $ScopeFile
 
#force to remove superscope if necessary
Remove-DhcpServerv4Scope -ComputerName $ServerName -ScopeId $ScopeId -Force
 
#update the subnet mask in the exported scope
[xml]$ScopeXml = Get-Content $ScopeFile
$ScopeXml.DHCPServer.IPv4.Scopes.Scope.SubnetMask = $SubnetMask
$ScopeXml.Save($ScopeFile)
 
#import modified scope after backing up current config (required)
Import-DhcpServer -ComputerName $ServerName -ScopeId $ScopeId -Leases -File $ScopeFile -BackupPath $ServerFileBackup