• Nagios 3.x or above is required for the multi-line output generated by this command.
• This service check will alarm if any scope is nearing the critical or warning threshold(s) specified command call.
• If you require per-scope or per-pool alarm configuration, you should use the original plugin created by Lars Michelsen.
• Performance Data has been commented out, but is available if you’d like to add it.
• Scopes that exist but are not in use (e.g. scopes exclusively used for reservations) are left out of this check. There is a conditional statement commented below that can report these scopes as being available, but with zero (0) free or used addresses, equaling zero (0) MAX available amount of addresses. This information isn’t really relevant, so I omitted it from being returned; however,  there is a count returned of configured and shown scopes (located at the bottom).

Feel free to use, reuse, or modify the script the suit your needs. There are other, similar plugins to accomplish the same thing, but most of these rely on NRPE, NSClient++, and netsh.

#! /bin/bash
# ##############################################################################
# check_dhcp_all_pools.sh - Nagios plugin
#
# This script querys a MS Windows DHCP-Server via SNMP v2 to fetch information about ALL available DHCP-Pools.
#
# Copyright (C) 2006, 2007 Lars Michelsen <lars@vertical-visions.de>,
# Modified 2012 by JRM
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,
#
# GNU General Public License: http://www.gnu.org/licenses/gpl-2.0.txt
#
# Report bugs to: lars@vertical-visions.de
#
# 2006-07-05 Version 0.2
# 2007-10-27 Version 0.3
#
# ##############################################################################

if [ $# -lt 2 ]; then
echo "check_dhcp_all_pools"
echo "Usage: $0 <host> <community> [<warn=10>] [<crit=5>]"
exit 3
fi

IP="$1"
COMMUNITY="$2"
WARN="$4"
CRIT="$5"
RET=0
RETW=0
RETC=0
STAT=( )
i=0

if [ ${#WARN} -lt 1 ]
then
WARN=10
fi

if [ ${#CRIT} -lt 1 ]
then
CRIT=5
fi

#Get the list of all scopes/subnets from the server:
TEMP=($( snmpwalk -c $COMMUNITY $IP .1.3.6.1.4.1.311.1.3.2.1.1.1 | cut -d " " -f4 ))

#Traverse array and get usage information per scope:
for i  in ${!TEMP[*]};do

POOL=${TEMP[$i]}

FREEOID=".1.3.6.1.4.1.311.1.3.2.1.1.3.$POOL"
USEDOID=".1.3.6.1.4.1.311.1.3.2.1.1.2.$POOL"

SNMP_RESULT=`snmpget -v 2c -c $COMMUNITY $IP $FREEOID`
FREE=`echo $SNMP_RESULT|cut -d " " -f4`

SNMP_RESULT=`snmpget -v 2c -c $COMMUNITY $IP $USEDOID`
USED=`echo $SNMP_RESULT|cut -d " " -f4`

MAX=`echo "$FREE+$USED" |bc`

if [ "$MAX" -ne 0 ]; then

PERCFREE=`echo "$FREE*100/$MAX" |bc`
PERCUSED=`echo "$USED*100/$MAX" |bc`

#DEBUG: echo "FREE: $FREE USED: $USED MAX: $MAX PERC: $PERCFREE,$PERCUSED"

if [ "$FREE" -le "$WARN" -a "$FREE" -gt "$CRIT" ]; then
STAT=( "${STAT[@]}" "Warning:\t$POOL - $PERCFREE free" )
RETW+=1
elif [ "$FREE" -le "$CRIT" ]; then
STAT=( "${STAT[@]}" "Critical:\t$POOL - $PERCFREE free" )
RETC+=2
else
STAT=( "${STAT[@]}" "OK:\t$POOL\t$PERCUSED% used" )
RET+=0
fi

#elif [ "$MAX" -eq 0 ]; then

#Debug for detecting 100% excluded ranges (reservations only):
#STAT=( "${STAT[@]}" "OK:\t$POOL\tNothing used, could be excluded" )

fi

# Performance-Data
#echo " | 'Scope Usage'=$PERCUSED%;$WARN;$CRIT;0;$MAX"
#echo -e " | $POOL OK - Usage: $PERCUSED% ($FREE Addresses of $MAX in pool free) \n"

done

#Evaluate return code:

if [ "$RET" -eq 0 ]; then
RET=0
echo -e "OK:\tAll scopes fine"
elif [ "$RETC" -gt 0 ]; then
RET=2
echo  -e "Critical: One or more scopes is nearing capacity"
elif [ "$RETW" -gt 0 ]; then
RET=1
echo -e "Warning: One or more scopes is nearing capacity"
fi

###### Second loop for long service output:

for I in ${!STAT[*]};do
echo -e ${STAT[$I]}
done

#Echo the total amount of scopes available vs those shown:
echo -e "\nShowing ${#STAT[@]} of ${#TEMP[@]} configured scopes"

exit $RET

I enjoyed the coffee cover included with the barebone system, but opted for something customized that would allow remote clients to phone in service-calls with all the important information (Local/WAN IP, MAC, FQDN, etc.) required for troubleshooting. Hope this helps someone out who might be looking for a better template than the one provided by Shuttle’s site.

DOWNLOAD MyKover Word Document Template (.DOC – Created w/ Microsoft Office 2003)