Understanding DNS Changes in Nutanix DR Recovery Plans

 1@echo off
 2:: -------------------------------------------------------------------------
 3:: vm_recovery.bat for Nutanix Disaster Recovery
 4:: -------------------------------------------------------------------------
 5:: Purpose:
 6::     This batch file initiates a PowerShell script to check and update 
 7::     the DNS configuration based on the current IP address. It logs all 
 8::     activities to a specified log file, creating a new log file with 
 9::     the current date if the previous log exists.
10::
11:: Description:
12::     - Checks if an existing log file (vm_recovery.log) is present.
13::       If it exists, renames it with the current date.
14::     - Calls the PowerShell script (check_dns.ps1) in the same directory
15::       to perform DNS checks and updates as required.
16::
17:: Requirements:
18::     - Must run with administrative privileges.
19::     - Requires PowerShell to be installed.
20::
21:: Version:
22::     1.0
23::
24:: Author:
25::     Mike Dent ([email protected])
26:: -------------------------------------------------------------------------
27
28set "scriptDir=%~dp0"
29set "logDir=C:\Program Files\Nutanix\scripts"
30set "logFile=%logDir%\vm_recovery.log"
31
32REM Check if log file exists and rename it with the current date if it does
33if exist "%logFile%" (
34    set "dateStr=%date:/=-%"
35    ren "%logFile%" "vm_recovery_%dateStr%.log"
36)
37
38REM Call the PowerShell script and pass the log directory
39powershell -ExecutionPolicy Bypass -File "%scriptDir%vm_recovery.ps1" -LogDir "%logDir%"

  1<#
  2.SYNOPSIS
  3    Nutanix Disaster Recovery DNS and IP Configuration Script
  4
  5.DESCRIPTION
  6    This script checks the current IP address against predefined subnets for Site A and Site B. If the IP address
  7    matches a subnet and the DNS servers are different from the defined configuration, it updates the DNS servers
  8    accordingly.
  9
 10.VERSION
 11    1.4
 12
 13.AUTHOR
 14    Mike Dent ([email protected])
 15
 16.NOTES
 17    - Called from vm_recovery.bat
 18    - Logs all actions to "C:\Program Files\Nutanix\scripts\vm_recovery.log"
 19    - Maintains a summary table in the log file of previous and updated DNS configurations
 20
 21.PARAMETER LogDir
 22    Directory to save the log file.
 23#>
 24
 25param (
 26    [string]$LogDir
 27)
 28
 29# Define the path for the log file
 30$LogFile = Join-Path -Path $LogDir -ChildPath "vm_recovery.log"
 31
 32# Function to write log entries
 33function Write-Log {
 34    param ([string]$Message)
 35    $timestamp = Get-Date -Format "yyyy-MM-dd HH:mm:ss"
 36    $entry = "$timestamp - $Message"
 37    Add-Content -Path $LogFile -Value $entry
 38}
 39
 40# Start logging
 41Write-Log "-------------------------------------------------------------"
 42Write-Log "DNS and IP Configuration Checker - Version 1.4"
 43Write-Log "Script initiated to verify and update DNS settings if needed"
 44Write-Log "-------------------------------------------------------------"
 45
 46# Define subnet and DNS information for Site A and Site B
 47$sites = @{
 48    "SiteA" = @{
 49        "Subnets" = @("172.x.x.0/24", "172.x.x0/24")
 50        "DNSServers" = @("172.x.x.250", "172.x.x.251")
 51    }
 52    "SiteB" = @{
 53        "Subnets" = @("172.x.x.0/24", "172.x.x0/24")
 54        "DNSServers" = @("172.x.x.250", "172.x.x.251")
 55    }
 56}
 57
 58# Get the current IP and DNS information
 59$currentIP = (Get-NetIPAddress -AddressFamily IPv4 | Where-Object {$_.IPAddress -ne "127.0.0.1"}).IPAddress
 60$currentDNS = (Get-DnsClientServerAddress -AddressFamily IPv4 | Select-Object -ExpandProperty ServerAddresses)
 61
 62Write-Log "Current IP Address: $currentIP"
 63Write-Log "Current DNS Servers Detected: $($currentDNS -join ', ')"
 64
 65# Store previous and new DNS values for logging
 66$previousDNS = $currentDNS
 67$newDNS = $null
 68
 69# Function to check if an IP belongs to a subnet
 70function Test-Subnet {
 71    param (
 72        [string]$IP,
 73        [string]$Subnet
 74    )
 75    $ipAddress = [System.Net.IPAddress]::Parse($IP)
 76    $subnetAddress, $prefixLength = $Subnet -split '/'
 77    $subnetMask = [System.Net.IPAddress]::Parse($subnetAddress)
 78    $networkBits = [int]$prefixLength
 79    $subnetBytes = $subnetMask.GetAddressBytes()
 80    $ipBytes = $ipAddress.GetAddressBytes()
 81
 82    for ($i = 0; $i -lt $networkBits / 8; $i++) {
 83        if ($ipBytes[$i] -ne $subnetBytes[$i]) {
 84            return $false
 85        }
 86    }
 87    return $true
 88}
 89
 90# Get the active network adapter’s InterfaceAlias
 91$activeAdapter = Get-NetAdapter | Where-Object {$_.Status -eq "Up"}
 92if (-not $activeAdapter) {
 93    Write-Log "Error: No active network adapter found. Exiting."
 94    exit
 95}
 96$interfaceAlias = $activeAdapter.InterfaceAlias
 97
 98Write-Log "Active Network Adapter InterfaceAlias: $interfaceAlias"
 99
100# Determine site based on current IP and update DNS if necessary
101foreach ($site in $sites.Keys) {
102    $siteData = $sites[$site]
103    $matchingSubnet = $siteData["Subnets"] | Where-Object { Test-Subnet -IP $currentIP -Subnet $_ }
104    
105    if ($matchingSubnet) {
106        Write-Log "Matched $currentIP to subnet $matchingSubnet in $site"
107        
108        # Strictly compare DNS server settings
109        $desiredDNS = $siteData["DNSServers"]
110        $dnsMismatch = ($currentDNS.Count -ne $desiredDNS.Count) -or ($currentDNS | Where-Object { $_ -notin $desiredDNS })
111
112        if (-not $dnsMismatch) {
113            Write-Log "DNS servers are already correctly configured for $site. No changes needed."
114            $newDNS = $currentDNS  # New DNS remains the same
115        }
116        else {
117            Write-Log "DNS servers mismatch detected. Expected: $($desiredDNS -join ', '), Current: $($currentDNS -join ', ')"
118            Write-Log "Attempting to update DNS servers to $($desiredDNS -join ', ') for $site"
119            
120            # Clear existing DNS servers
121            try {
122                Set-DnsClientServerAddress -InterfaceAlias $interfaceAlias -ServerAddresses @()
123                Write-Log "Cleared existing DNS servers on $interfaceAlias."
124                
125                # Set new DNS servers
126                Set-DnsClientServerAddress -InterfaceAlias $interfaceAlias -ServerAddresses $desiredDNS -ErrorAction Stop
127                Write-Log "DNS servers updated successfully to $($desiredDNS -join ', ') on $interfaceAlias."
128                $newDNS = $desiredDNS  # New DNS after update
129            }
130            catch {
131                Write-Log "Error: Failed to update DNS servers. $_"
132            }
133
134            # Verify the DNS settings after update
135            $updatedDNS = (Get-DnsClientServerAddress -InterfaceAlias $interfaceAlias -AddressFamily IPv4).ServerAddresses
136            if ($updatedDNS -join ',' -eq $desiredDNS -join ',') {
137                Write-Log "DNS update verification passed: $($updatedDNS -join ', ')"
138            } else {
139                Write-Log "Warning: DNS update verification failed. Expected: $($desiredDNS -join ', ') | Actual: $($updatedDNS -join ', ')"
140            }
141        }
142        break
143    }
144}
145
146# Summary table in log file
147Write-Log "-------------------------------------------------------------"
148Write-Log "Summary of DNS Configuration Changes"
149Write-Log "-------------------------------------------------------------"
150Write-Log "| Parameter       | Previous Value             | Current Value           |"
151Write-Log "|-----------------|---------------------------|--------------------------|"
152Write-Log "| IP Address      | $currentIP                 | $currentIP               |"
153Write-Log "| DNS Servers     | $($previousDNS -join ', ') | $($newDNS -join ', ')   |"
154Write-Log "-------------------------------------------------------------"
155
156Write-Log "DNS and IP check completed."