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dhcp_server_watchdog.bat
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dhcp_server_watchdog.bat
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:: Purpose: DHCP server Watchdog & Failover script. Read notes below
:: Requirements: 1. Domain administrator credentials & "Logon as a batch job" rights
:: 2. Proper firewall configuration to allow connection
:: 3. Proper permissions on the DHCP backup directory
:: Author: vocatus on reddit.com/r/sysadmin ( vocatus.gate@gmail.com ) // PGP key ID: 0x07d1490f82a211a2
:: Version: 1.3.1 * Rename VERSION and UPDATED to SCRIPT_VERSION and SCRIPT_UPDATED, respectively
:: 1.0.0 Initial write
:: Notes: I wrote this script after failing to find a satisfactory method of performing
:: watchdog/failover between two Windows Server 2008 R2 DHCP servers.
::
:: This script has two modes: "Watchdog" and "Failover."
:: - Watchdog checks the status of the remote DHCP service, logs it, and then grabs the remote DHCP db backup file and imports it.
:: - Failover mode is activated when the script cannot determine the status of the remote DHCP server. The script then activates
:: the local DHCP server with the latest backup copy it successfully retrieved from the primary server.
::
:: Instructions: 1. Tune the variables in this script to your desired backup location and frequency
:: 2. On the primary server: set the DHCP backup interval to your desired backup frequency. The value is in minutes; I recommend 5 minutes.
:: You do this by modifying this registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DHCPServer\Parameters\BackupInterval
:: 3. On the backup server: set this script to run as a scheduled task. I recommend every 10 minutes.
:: Notice:
:: !! Make sure to set it only to run if it isn't already running! If there is a failover you could have
:: Task Scheduler spawn a new instance of the script every n minutes and end up with hundreds of copies
:: of this script running.
SETLOCAL
:::::::::::::::
:: VARIABLES :: -------------- These are the defaults. Change them if you so desire. --------- ::
:::::::::::::::
:: Rules for variables:
:: * NO quotes! (bad: "c:\directory\path" )
:: * NO trailing slashes on the path! (bad: c:\directory\ )
:: * Spaces are okay (okay: c:\my folder\with spaces )
:: * Network paths are okay (okay: \\server\share name )
:: ( \\172.16.1.5\share name )
:: Remote server is the PRIMARY DHCP server we're watching. Use a hostname or IP address.
set REMOTE_SERVER=YOUR-DHCP-SERVER
:: Location of the automatic DHCP backup file on the primary server. Windows generates this automatically.
:: Best practice is to leave this alone, unless you have a custom backup location.
:: The script builds the backup line like this: \\%REMOTE_SERVER%\c$\%REMOTE_BACKUP_PATH%
set REMOTE_BACKUP_PATH=Windows\system32\dhcp\backup
:: Location of the operational DHCP database files on the remote (primary) server.
:: Best practice is to leave this alone, unless you have a custom location. Changing this will break the
:: function that re-uploads the most current db back to the primary server after a failure. This doesn't
:: ruin the script, but if the backup server passed out any IP's while the primary server was down, the
:: primary server won't know about them when it comes back up.
set REMOTE_OPERATING_PATH=Windows\system32\dhcp
:: Location of your backup/standby file. I normally copy directly to my backup server's DHCP directory.
:: The script builds the local backup line like this: c:\windows\system32\dhcp\[backup folders]
set LOCAL_BACKUP_PATH=%SystemRoot%\system32\dhcp
:: When a failover is triggered, how many seconds should we wait in between each attempt to contact the primary server again?
set FAILOVER_RECHECK_DELAY=10
:: Log options. Don't put an extension on the log file name. (Important!) The script sets this later on.
set LOGPATH=%SystemDrive%\Logs
set LOGFILE=%COMPUTERNAME%_DHCP_watchdog
:: Max log file size allowed (in bytes) before rotation and archive. I recommend setting this to 2 MB (2097152).
:: Example: 524288 is half a megabyte (~500KB)
set LOG_MAX_SIZE=10485760
:: --------------------------- Don't edit anything below this line --------------------------- ::
:::::::::::::::::::::
:: PREP AND CHECKS ::
:::::::::::::::::::::
@echo off
cls
set SCRIPT_VERSION=1.3.1
set SCRIPT_UPDATED=2014-09-11
:: Get the date into ISO 8601 standard date format (yyyy-mm-dd) so we can use it
FOR /f %%a in ('WMIC OS GET LocalDateTime ^| find "."') DO set DTS=%%a
set CUR_DATE=%DTS:~0,4%-%DTS:~4,2%-%DTS:~6,2%
title [DHCP Server Watchdog v%SCRIPT_VERSION%]
:::::::::::::::::::::::
:: LOG FILE HANDLING :: - This section handles the log file
:::::::::::::::::::::::
:: Make the logfile if it doesn't exist
if not exist %LOGPATH% mkdir %LOGPATH%
if not exist %LOGPATH%\%LOGFILE%.log goto new_log
:: Check log size. If it hasn't exceeded our size limit, jump straight to Watchdog mode
for %%R in (%LOGPATH%\%LOGFILE%.log) do if %%~zR LSS %LOG_MAX_SIZE% goto newrun
:: However, if the log was too big, go ahead and rotate it.
pushd %LOGPATH%
del %LOGFILE%.ancient 2>NUL
rename %LOGFILE%.oldest %LOGFILE%.ancient 2>NUL
rename %LOGFILE%.older %LOGFILE%.oldest 2>NUL
rename %LOGFILE%.old %LOGFILE%.older 2>NUL
rename %LOGFILE%.log %LOGFILE%.old 2>NUL
popd
:: And then create the header for the new log file
:new_log
echo ------------------------------------------------------------------------------------->> %LOGPATH%\%LOGFILE%.log
echo Initializing new DHCP Server Watchdog log on %CUR_DATE% at %TIME%, max log size %LOG_MAX_SIZE% bytes>> %LOGPATH%\%LOGFILE%.log
echo ------------------------------------------------------------------------------------->> %LOGPATH%\%LOGFILE%.log
echo.>> %LOGPATH%\%LOGFILE%.log
:: New run section - if we just launched the script, write a header for this run
:newrun
echo ------------------------------------------------------------------------------------->> %LOGPATH%\%LOGFILE%.log
echo DHCP Server Watchdog v%SCRIPT_VERSION%, %CUR_DATE%>> %LOGPATH%\%LOGFILE%.log
echo Running as %USERDOMAIN%\%USERNAME% on %COMPUTERNAME%>> %LOGPATH%\%LOGFILE%.log
echo.>> %LOGPATH%\%LOGFILE%.log
echo Job Options>> %LOGPATH%\%LOGFILE%.log
echo Log location: %LOGPATH%\%LOGFILE%.log>> %LOGPATH%\%LOGFILE%.log
echo Log max size: %LOG_MAX_SIZE% bytes>> %LOGPATH%\%LOGFILE%.log
echo Watching primary server: %REMOTE_SERVER%>> %LOGPATH%\%LOGFILE%.log
echo Mirroring this DHCP db: %REMOTE_BACKUP_PATH%>> %LOGPATH%\%LOGFILE%.log
echo Local backup location: %LOCAL_BACKUP_PATH%>> %LOGPATH%\%LOGFILE%.log
echo ------------------------------------------------------------------------------------->> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Starting Watchdog mode.>> %LOGPATH%\%LOGFILE%.log
echo.
echo DHCP Server Watchdog v%SCRIPT_VERSION%
echo Running as: %USERDOMAIN%\%USERNAME% on %COMPUTERNAME%
echo Log: %LOGPATH%\%LOGFILE%.log
:::::::::::::::::::
:: WATCHDOG MODE ::
:::::::::::::::::::
:watchdog
:: Ping the server to see if it's up
echo.
echo Verifying proper operation of DHCP server on %REMOTE_SERVER%, please wait...
echo.
echo %CUR_DATE% %TIME% Pinging %REMOTE_SERVER%...>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Pinging %REMOTE_SERVER%...
ping %REMOTE_SERVER% -n %FAILOVER_RECHECK_DELAY% >NUL
if %ERRORLEVEL%==1 echo %CUR_DATE% %TIME% WARNING %REMOTE_SERVER% failed to respond to ping. && echo %CUR_DATE% %TIME% WARNING %REMOTE_SERVER% failed to respond to ping.>> %LOGPATH%\%LOGFILE%.log
if not %ERRORLEVEL%==1 echo %CUR_DATE% %TIME% SUCCESS %REMOTE_SERVER% responded to ping. && echo %CUR_DATE% %TIME% SUCCESS %REMOTE_SERVER% responded to ping.>> %LOGPATH%\%LOGFILE%.log
:: Check & Log
echo %CUR_DATE% %TIME% Checking DHCP server status on %REMOTE_SERVER%...>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Checking DHCP server status on %REMOTE_SERVER%...
:: Reset ERRORLEVEL back to 0
ver > NUL
:: Use "SC" to check the status of "Dhcpserver" service, find the "RUNNING" state, and act accordingly based on the return code
%WINDIR%\System32\sc.exe \\%REMOTE_SERVER% query Dhcpserver | find "RUNNING" >NUL
if %ERRORLEVEL%==0 echo %CUR_DATE% %TIME% SUCCESS The DHCP service is running on %REMOTE_SERVER%.>> %LOGPATH%\%LOGFILE%.log
if %ERRORLEVEL%==0 echo %CUR_DATE% %TIME% SUCCESS The DHCP service is running on %REMOTE_SERVER%.
:: This section only executes if the test failed.
if not %ERRORLEVEL%==0 (
echo %CUR_DATE% %TIME% FAILURE The DHCP service is not running on %REMOTE_SERVER%.>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Activating failover procedure. Local DHCP server will be initialized using most recent successful backup.>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% FAILURE The DHCP service is not running on %REMOTE_SERVER%.
echo %CUR_DATE% %TIME% Activating failover procedure. Local DHCP server will be initialized using most recent successful backup.
goto failover
)
:: Reset ERRORLEVEL back to 0
ver > NUL
:: Fetch
echo %CUR_DATE% %TIME% Fetching DHCP database backup from %REMOTE_SERVER%...>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Fetching DHCP database backup from %REMOTE_SERVER%...
xcopy "\\%REMOTE_SERVER%\c$\%REMOTE_BACKUP_PATH%\*" "%LOCAL_BACKUP_PATH%\backup_new_pending\" /E /Y /Q >NUL
:: If the copy SUCCEEDED, this executes
if %ERRORLEVEL%==0 (
echo %CUR_DATE% %TIME% SUCCESS Backup fetched from %REMOTE_SERVER%.>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% SUCCESS Backup fetched from %REMOTE_SERVER%.
echo %CUR_DATE% %TIME% Rotating database backups...>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Rotating database backups...
:: Rotate backups and use newest copy
rmdir /S /Q %LOCAL_BACKUP_PATH%\backup5
if exist "%LOCAL_BACKUP_PATH%\backup4" move /Y "%LOCAL_BACKUP_PATH%\backup4" "%LOCAL_BACKUP_PATH%\backup5"
if exist "%LOCAL_BACKUP_PATH%\backup3" move /Y "%LOCAL_BACKUP_PATH%\backup3" "%LOCAL_BACKUP_PATH%\backup4"
if exist "%LOCAL_BACKUP_PATH%\backup2" move /Y "%LOCAL_BACKUP_PATH%\backup2" "%LOCAL_BACKUP_PATH%\backup3"
if exist "%LOCAL_BACKUP_PATH%\backup" move /Y "%LOCAL_BACKUP_PATH%\backup" "%LOCAL_BACKUP_PATH%\backup2"
move /Y "%LOCAL_BACKUP_PATH%\backup_new_pending" "%LOCAL_BACKUP_PATH%\backup" >NUL
echo %CUR_DATE% %TIME% Database backups rotated.>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Database backups rotated.
)
:: If the copy FAILED, this executes:
if not %ERRORLEVEL%==0 (
echo %CUR_DATE% %TIME% WARNING There was an error copying the backup from %REMOTE_SERVER%.>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% You may want to look into this since we were able to check the DHCPserver service status but the file copy failed.>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Skipping new database import due to copy failure.>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Job complete with errors.>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% WARNING There was an error copying the backup from %REMOTE_SERVER%.
echo %CUR_DATE% %TIME% You may want to look into this since we were able to check the DHCPserver service status but the file copy failed.
echo %CUR_DATE% %TIME% Skipping new database import due to copy failure.
echo %CUR_DATE% %TIME% Job complete with errors.
)
:: Import database
echo %CUR_DATE% %TIME% Starting local DHCP server to import new database...>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Starting local DHCP server to import new database...
net start Dhcpserver
echo %CUR_DATE% %TIME% Local DHCP server running. Performing import...>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Local DHCP server running. Performing import...
netsh dhcp server restore "%LOCAL_BACKUP_PATH%\backup"
echo %CUR_DATE% %TIME% Import complete.>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Import complete.
echo %CUR_DATE% %TIME% Stopping local DHCP server...>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Stopping local DHCP server...
sc stop Dhcpserver
echo %CUR_DATE% %TIME% Local DHCP server stopped.>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Local DHCP server stopped.
echo %CUR_DATE% %TIME% SUCCESS Job complete, DHCP database backed up and ready for use. Exiting.>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% SUCCESS Job complete, DHCP database backed up and ready for use. Exiting.
goto EOF
:::::::::::::::::::
:: FAILOVER MODE ::
:::::::::::::::::::
:failover
:: Log this AND display to console
echo %CUR_DATE% %TIME% WARNING Failover activated.>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Starting local DHCP server using most recent successful backup...>> %LOGPATH%\%LOGFILE%.log
echo.
echo %CUR_DATE% %TIME% WARNING Could not contact primary DHCP server %REMOTE_SERVER%. Failover activated.
echo %CUR_DATE% %TIME% Starting local DHCP server using most recent successful backup...
echo.
net start Dhcpserver
echo %CUR_DATE% %TIME% Local DHCP server started.>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Entering monitoring loop. Checking if %REMOTE_SERVER% is back up every %FAILOVER_RECHECK_DELAY% seconds...>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Local DHCP server started.
echo %CUR_DATE% %TIME% Entering monitoring loop. Checking if %REMOTE_SERVER% is back up every %FAILOVER_RECHECK_DELAY% seconds...
:failover_loop
:: First we ping the server
ping %REMOTE_SERVER% -n 5 >NUL
:: If no ping response, this section executes
IF NOT %ERRORLEVEL%==0 (
echo %CUR_DATE% %TIME% FAILURE No ping response from %REMOTE_SERVER%. Waiting %FAILOVER_RECHECK_DELAY% seconds to check again.>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% FAILURE No ping response from %REMOTE_SERVER%. Waiting %FAILOVER_RECHECK_DELAY% seconds to check again.
ping localhost -n %FAILOVER_RECHECK_DELAY% >NUL
goto failover_loop
)
:: If yes ping response, this section executes
:: This declaration is required to get the nested IF ERRORLEVEL test to function correctly
SETLOCAL ENABLEDELAYEDEXPANSION
if not %ERRORLEVEL%==1 (
echo %CUR_DATE% %TIME% NOTICE %REMOTE_SERVER% is responding to pings.>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% NOTICE %REMOTE_SERVER% is responding to pings.
echo %CUR_DATE% %TIME% Checking DHCP server status on %REMOTE_SERVER%...>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Checking DHCP server status on %REMOTE_SERVER%...
:: This section checks to see if the Dhcpserver service is back up and acts accordingly
%WINDIR%\System32\sc.exe \\%REMOTE_SERVER% query Dhcpserver | find "RUNNING" >NUL
:: The exclamation points around ERRORLEVEL here prevent it from incorrectly being expanded using the external ERRORLEVEL results from the first IF statement
if !ERRORLEVEL!==0 (
echo %CUR_DATE% %TIME% SUCCESS The DHCP service is running on %REMOTE_SERVER%.>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% SUCCESS The DHCP service is running on %REMOTE_SERVER%.
echo %CUR_DATE% %TIME% Primary DHCP server %REMOTE_SERVER% is back up. Beginning recovery procedures...>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Primary DHCP server %REMOTE_SERVER% is back up. Beginning recovery procedures...
:: Back up the database that we've been running temporarily while the primary server was down
echo %CUR_DATE% %TIME% Exporting the current DHCP database...>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Exporting the current DHCP database...
netsh dhcp server backup %TEMP%\DHCP-RECOVERY
:: Stop our local server since we're done performing DHCP server duties
echo %CUR_DATE% %TIME% Stopping local DHCP server...>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Stopping local DHCP server...
sc stop Dhcpserver
:: Send the database back to the primary server
echo %CUR_DATE% %TIME% Uploading current DHCP database to %REMOTE_SERVER%...>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Uploading current DHCP database to %REMOTE_SERVER%...
xcopy "%TEMP%\DHCP-RECOVERY\*" "\\%REMOTE_SERVER%\c$\%REMOTE_OPERATING_PATH%\DHCP-RECOVERY\" /S /Y /Q 2>NUL
:: Import the current database on the primary server
echo %CUR_DATE% %TIME% Importing current DHCP database on %REMOTE_SERVER%...>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Importing current DHCP database on %REMOTE_SERVER%...
netsh dhcp server \\%REMOTE_SERVER% restore "\\%REMOTE_SERVER%\c$\%REMOTE_OPERATING_PATH%\DHCP-RECOVERY"
:: force a delay to let it stop
ping -n 4 localhost >NUL
:: Spin the primary server back up. For some reason we have to run the command twice for it to actually start. Don't ask.
echo %CUR_DATE% %TIME% Restarting DHCP server on %REMOTE_SERVER%...>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Restarting DHCP server on %REMOTE_SERVER%...
sc \\%REMOTE_SERVER% stop Dhcpserver
ping localhost -n 8 >NUL
sc \\%REMOTE_SERVER% start Dhcpserver
ping localhost -n 5 >NUL
sc \\%REMOTE_SERVER% query Dhcpserver
ping localhost -n 8 >NUL
sc \\%REMOTE_SERVER% start Dhcpserver
REM :: Check to make sure it's working
REM echo %CUR_DATE% %TIME% Verifying functionality on primary server...>> %LOGPATH%\%LOGFILE%.log
REM echo %CUR_DATE% %TIME% Verifying functionality on primary server...
REM sc \\%REMOTE_SERVER% query Dhcpserver | find "RUNNING"
REM if not %ERRORLEVEL%==0 echo %CUR_DATE% %TIME% FAILURE DHCP server on %REMOTE_SERVER% is not running. You should investigate this manually.>> %LOGPATH%\%LOGFILE%.log
REM if %ERRORLEVEL%==0 echo %CUR_DATE% %TIME% SUCCESS DHCP server on %REMOTE_SERVER% is up and running. Recovery complete.>> %LOGPATH%\%LOGFILE%.log
:: Clean up
rmdir /S /Q %TEMP%\DHCP-RECOVERY
:: Done.
echo %CUR_DATE% %TIME% Exiting.>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% Exiting.
goto EOF
)
)
ENDLOCAL
:: If the host responds to pings but the DHCP service isn't running, this executes
echo %CUR_DATE% %TIME% FAILURE %REMOTE_SERVER% is responding to pings, but DHCP isn't responding (yet?). Will try again in %FAILOVER_RECHECK_DELAY% seconds.>> %LOGPATH%\%LOGFILE%.log
echo %CUR_DATE% %TIME% FAILURE %REMOTE_SERVER% is responding to pings, but DHCP isn't responding (yet?). Will try again in %FAILOVER_RECHECK_DELAY% seconds.
ver >NUL
goto failover_loop
ENDLOCAL
echo.>> %LOGPATH%\%LOGFILE%.log
:EOF