Tag Archives: NMS

Zabbix: a lightweight dynamic template for SNMP routers

I built the following Zabbix template to monitor small routers, with just two interfaces (WAN and LAN), which have been deployed as CPE for some customers.

What I needed was only interfaces monitoring, such as traffic, packets, status, but I needed to configure it for many etherogeneous devices, that means different SNMP indexing and naming.

I decided to build a small SNMP-based template using dynamic parameters and host macros.

Each template’s item has an SNMP OID value containing a macro reference:

Description: LAN - Description
Type: SNMPv2 agent
Key: ifDescr-LAN

Description: LAN - In Octets
Type: SNMPv2 agent
Key: ifInOctets-LAN

Description: WAN - Description
Type: SNMPv2 agent
Key: ifDescr-WAN


On each host you apply this template to you need to add two macros, {$LAN_IF_IDX} and {$WAN_IF_IDX}, containing the value of the LAN and WAN interface SNMP index:

In order to understand which value to use in the macro you can “ask it” to your router or run a snmpwalk on it:

CiscoRouter#show snmp mib ifmib ifindex FastEthernet 0/0
Interface = FastEthernet0/0, Ifindex = 1

root@NMS:~# snmpwalk -v 2c -c public .
iso. = STRING: "FastEthernet0/0"
iso. = STRING: "FastEthernet0/1"
iso. = STRING: "VoIP-Null0"
iso. = STRING: "Null0"
iso. = STRING: "Loopback1"

The template includes interfaces description, status, traffic (in bps and packets per second), a trigger to detect status transition and graphs.

You can find the Zabbix Template_Lightweight_Dynamic_SNMPv2_Router here; instructions about importing the template can be found on the Zabbix documentation web site.

Zabbix: send SMS using gammu-smsd

Recently I needed to setup a Zabbix distribution with SMS notifications. I had a Momo Design MD-@ USB Internet key to be used as GSM modem, with a BT Italia (Vodafone) SIM card. I used the 1.8.5 version of Zabbix, installed using the apt tool on a Ubuntu 11.10.

The Zabbix built-in SMS notification system seemed to have a bug, which cause a triple notification to be sent on every trigger action (bug ID ZBX-3507), so I preferred to use an external (custom) script and a third party tool: gammu-smsd.

This daemon connects to the GSM modem and listens for an outgoing queue; when you need to send a message, you just have to “inject” it into its queue, then it does the rest.


As soon as I plugged the USB key into the server, Ubuntu recognized it:

Oct 27 13:57:08 MyMachineName kernel: [764858.260009] usb 4-1: new full speed USB device number 2 using uhci_hcd
Oct 27 13:57:08 MyMachineName kernel: [764858.481158] cdc_acm 4-1:1.0: ttyACM0: USB ACM device
Oct 27 13:57:08 MyMachineName kernel: [764858.484118] usbcore: registered new interface driver cdc_acm
Oct 27 13:57:08 MyMachineName kernel: [764858.484121] cdc_acm: USB Abstract Control Model driver for USB modems and ISDN adapters

Then I installed gammu-smsd and edited its configuration file:

apt-get install gammu-smsd
cat /etc/gammu-smsdrc

# Configuration file for Gammu SMS Daemon

# Gammu library configuration, see gammurc(5)
# Please configure this!
port = /dev/ttyACM0
connection = at
# Debugging
logformat = textall

# SMSD configuration, see gammu-smsdrc(5)
service = files
logfile = /var/log/gammu-smsd
# Increase for debugging information
debuglevel = 0
ReceiveFrequency = 300
# Paths where messages are stored
inboxpath = /var/spool/gammu/inbox/
outboxpath = /var/spool/gammu/outbox/
sentsmspath = /var/spool/gammu/sent/
errorsmspath = /var/spool/gammu/error/

The port parameter is the device where the modem is mapped. This may change on other system.

I changed the logfile parameter also, because by default it is configured to log to syslog. You need to give the right permissions to it:

chmod a+rw /var/log/gammu-smsd

The ReceiveFrequency is used to tell gammu-smsd how often to check for incoming SMS; by default it is every 1 second, but in my case I didn’t need to receive SMS, so I raised it to 5 minutes.

An important parameter is PIN on the [smsd] section: in my case I removed the PIN check from my SIM card, so I didn’t use it in the configuration file.

In order to avoid “Cannot open file” errors, I also granted access to the device to everyone:

chmod a+rw /dev/ttyACM0

At this time I reloaded gammu-smsd and tested the configuration:

/etc/init.d/gammu-smsd restart
echo "Test message" | gammu-smsd-inject TEXT 335123456

(replace 335123456 with your mobile phone number!)

The gammu-smsd-monitor utility let you to check your modem status too.

In order to rotate gammu-smsd log file, I wrote a logrotate.d configuration file too:

cat /etc/logrotate.d/gammu-smsd
/var/log/gammu-smsd {
    rotate 7

Zabbix configuration

As first I configured a new media type using the Zabbix administration front-end:

Administration / Media types -> Create Media Type

Description: SMS-via-gammu
Type: Script
Script name: sendsms

sendsms is the name of the external script I used for my custom notification system.

Then I configured the new media type for my Zabbix user:

Administration / Users -> select Users in the top right corner – edit your user Media: Add

Type: SMS-via-gammu
Send to: 335123456
When active, Use if severity: as you wish
Status: Enabled

Of course, I had an Action configured too, but for more information I suggest you to read about it on the official documentation page.

In order to configure Zabbix to use external notification scripts, I verified that the AlertScriptsPath was present in the configuration file:

cat /etc/zabbix/zabbix_server.conf | grep AlertScriptsPath

/etc/zabbix/alert.d is the directory where notifications script have to be.

Then I added the zabbix user to the gammu group, in order to give it the right permissions to inject messages into the outgoing gammu queue…

adduser zabbix gammu

… then I restarted Zabbix:

/etc/init.d/zabbix-server restart

This is the script I used to inject Zabbix notifications into the gammu outgoing queue (/etc/zabbix/alert.d/sendsms):


# $1    recipient
# $2    subject
# $3    message

TMPFILE=`mktemp -t`

echo "$3" >> $TMPFILE

cat $TMPFILE | gammu-smsd-inject TEXT $1

chmod a+x /etc/zabbix/alert.d/sendsms

At this time I tested it by creating a new trigger with fake values (temperature < 100 °C, or everything else could let an action to be raised).


Zabbix.com: Configuration page on the official documentation site

gammu-smsd: Gammu SMSD

Book review: Zabbix 1.8 Network Monitoring

Zabbix is a good Network Monitoring System, recently grown up to version 1.8. The book I was pleased to review is an easy guide to go deep into its mechanisms and to discover its many features.

The book covers every aspect of Zabbix, from the installation process to distributed monitoring, with a in-depth coverage of hosts monitoring techniques and user notification system. Many practical examples and screenshots help the reader to configure the system and have a fully working setup in a few minutes.

A whole chapter is dedicated to the SNMP integration, with a good explaination of the protocol and very practical tips about the use of Net-SNMP suite and MIBs. The author also included a good tutorial about the setup of a traps handling procedure with hosts binding.

Two more noteworthy chapters are about the use of templates and macros to simplify the configuration of Zabbix, and advanced monitoring, such as using external scripts or data already gathered by other systems.

If you plan to use Zabbix and you are starting from scratch, or even if you already use it but you want to deepen some aspects, I really suggest you to have a look at this book! In the meantime, here you can find a sample chapter: Getting your first Notification (PDF).

My two pennies worth 😉


Title: Zabbix 1.8 Network Monitoring
Language: English
Paperback: 428 pages [ 235mm x 191mm ]
Release Date: March 2010
ISBN: 184719768X
ISBN 13: 978-1-847197-68-9
Author(s): Rihards Olups
More info: Packt Publishing web site

NetFlow: installation and configuration of NFDUMP and NfSen on Debian

After the brief overview about the installation of flow-tools and FlowViewer, in this post I’d like to share my experience about the setup of a basic solution based on another pair of tools: NFDUMP and NfSen. As always on my posts, the starting point is a fresh Debian 5.0 setup.

UPDATE: you may be interested in FlowGraph too, a tool that allows to dynamically build graphs based on previously collected netflow data and to use them in a web-based front-end, adding details about Autonomous System Number holders, IPv4 and IPv6 prefixes, inet(6)num objects, netnames from RIPE Stat.

Read more …

NetFlow: weird TCP flags in FlowViewer and flow-print?

Working with FlowViewer and flow-print (from the flow-tools suite), if you filter some NetFlow data by TCP flags you may notice a weird behaviour, like the one in the following picture:

FlowViewer - TCP Flags

Here I applied a filter on TCP Flags = 27, but on the output I had the “Fl” (Flag) column reporting 3! What’s up? Is 3 a kind of alias for 27? Is this a math puzzle? None of this!

Read more …