Zabbix, SNMP traps mapped to the right host

In my opinion Zabbix is a really good NMS, but it’s lacking on SNMP traps handling.

Traps can be received using Net-SNMP suite and snmptrap.sh, a script released within the misc directory of Zabbix.

This is how it works: snmptrapd starts listening on port UDP 162, receives traps and sends them to a handler, which runs the script and pass trap information to its standard input. Finally, the script runs zabbix_sender to send information to the Zabbix server. On Zabbix, you can setup a fake Host with an Item of type “ZABBIX Trapper”: in the original script, both host and item’s key are referenced as snmptraps.

It works! The problem is that, whatever the sender is, trap data is always binded to one host: snmptraps.

zabbix_sender, used to send traps information to the server, can’t translate IP address to hostname:

# ./zabbix_sender -h

ZABBIX send v1.6.2 (16 January 2009)

usage: zabbix_sender [-Vhv] {[-zpsI] -ko | [-zpI] -i } [-c ]
Options:

[cut]

-s --host  Specify host name.
Host IP address and DNS name will not work.

[cut]

So, we need to translate the sender’s IP address to its Zabbix hostname, in order to runs zabbix_sender with the right -s option value.

I make a very simple script to build an { IP / Zabbix hostname } file, using mysql client:

DST="/home/zabbix/zabbix-1.6.2/misc/snmptrap/zabbixhosts"
mysql --batch --silent -e "SELECT CONCAT( '[', IP, ']', Host )
FROM zabbix.hosts WHERE IP <> '' AND IP <> '0.0.0.0'" > $DST

Running this script every 30 minutes I have a file containing pairs of IP/HostName such these:

[192.168.0.1]MYWEBSERVER
[192.168.0.2]MYMAILSERVER

With few changes to the original script I can send traps to the right Zabbix host, grabbing the hostname from the mySql dump (zabbixhosts):

# CONFIGURATION

ZABBIX_SERVER="127.0.0.1";
ZABBIX_PORT="10051";

# path to zabbix_sender
ZABBIX_SENDER="/home/zabbix/zabbix-1.6.2/src/zabbix_sender/zabbix_sender";

# path to zabbixhosts, containing IP/hostname pairs
ZABBIX_HOSTSFILE="/home/zabbix/zabbix-1.6.2/misc/snmptrap/zabbixhosts"

# item key used to grab snmp data
KEY="snmptrap";

# used if the script can't find the hostname
DEFAULTHOST="Default_Trapper";

# END OF CONFIGURATION

read hostname
read ip
read uptime
read oid
read var1
read var2
read var3

oid=`echo $oid|cut -f2 -d' '`

# get hostname from the mySql dump
ZABBIX_HOST=`grep "[$hostname]" $ZABBIX_HOSTSFILE`

if [ $? -eq 0 ]; then
        hostname=`echo "$ZABBIX_HOST" | cut -f2 -d]`
else
        hostname="$DEFAULTHOST"
fi

str="$oid $var1 $var2 $var3"

result=`$ZABBIX_SENDER -z $ZABBIX_SERVER -p $ZABBIX_PORT
-s $hostname -k $KEY -o "$str"`

With this script you need an Item with type=”ZABBIX Trapper” and key=”snmptrap” for each host you want trap handling. You can also create a template and attach it to hosts you want to monitor.
You can create triggers based on snmp trap content as you want.

I use crontab to update the IP-to-hostname file two times each hour.

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