Last of the hurdles was to get data from Asterisk in order to send to Zabbix, however the traditional way of loading the res_snmp.so module in Asterisk was not available, as while the PBX in question utilises Asterisk, its buried under proprietary licensing and a non-standard api, therefore being unable to either add the SNMP module or to query it.

If you are experiencing a similar situation, here is how to extract some stats from Asterisk 16 using SNMP, but without the SNMP module…

Despite not being able edit Asterisk code directly, SSH access and the Asterisk CLI is available, so can run commands to return a snapshot of PBX activity.

The following commands can be run to output some valuable info:

asterisk -rx ‘pjsip show endpoints’ returns total number and current online endpoints, as well as reported user agent of device.

asterisk -rx ‘core show channels verbose’ gives us a list of active channels and current point in an inbound call flow, along with a counter of completed calls.

asterisk -rx ‘pjsip show channelstats’ is similar to ‘show channels verbose’, but includes the codec in use, helpful to determine if the system is transcoding.

Scripts

To get and output just the info required, a script can be created to parse the command output and list each value on a new line.

Create the three files below and paste the code in.
In this example I saved to /usr/local……

asterisk_chan.sh

command_output=$(asterisk -rx 'core show channels')

active=$(echo "$command_output" | grep -oE '[0-9]+ active channels' | grep -oE '[0-9]+')
processed=$(echo "$command_output" | grep -oE '[0-9]+ calls processed' | grep -oE '[0-9]+')

echo "$active"
echo "$processed"

asterisk_chanstat.sh

command_output=$(asterisk -rx 'pjsip show channelstats')

opus=$(echo "$command_output" | grep 'opus' | (wc -l))
g722=$(echo "$command_output" | grep 'g722' | (wc -l))
alaw=$(echo "$command_output" | grep 'alaw' | (wc -l))
ulaw=$(echo "$command_output" | grep 'ulaw' | (wc -l))
g729=$(echo "$command_output" | grep 'ulaw' | (wc -l))
total=$(echo "$command_output" | grep -oP 'Objects found: \K\d+' || echo 0)

echo "$opus"
echo "$g722"
echo "$alaw"
echo "$ulaw"
echo "$g729"
echo "$total"

asterisk_endpoint.sh

command_output=$(asterisk -rx 'pjsip show endpoints')

avail=$(echo "$command_output" | grep 'Avail' | (wc -l))
total=$(( $(echo "$command_output" | grep -c 'Endpoint') - 1 ))

echo "$avail"
echo "$total"

Saved, they need to be made executable, add the execute flag to each file…

chmod +x /usr/local/asterisk_chan.sh
chmod +x /usr/local/asterisk_chanstat.sh
chmod +x /usr/local/asterisk_endpoint.sh

SNMP extend_sh

SNMP has an extension feature to add and poll your own custom data, to take advantage of this the snmp.d.conf file need to include reference and path to the scripts. At the bottom of snmpd.conf, add the following lines…

extend-sh asterisk_chan /usr/local/share/snmp/rps/asterisk_chan.sh
extend-sh asterisk_chanstat /usr/local/share/snmp/rps/asterisk_chanstat.sh
extend-sh asterisk_endpoint /usr/local/share/snmp/rps/asterisk_endpoint.sh

Restart snmpd to load changes…

Gentoo:

/etc/init.d/snmpd restart

RHEL:

systemctl restart snmpd

Testing

Using snmpget command locally or on your collector machine, test that its working..

snmpget -c }your-community} -v 2c {ip-address} 'NET-SNMP-EXTEND-MIB::nsExtendOutLine."asterisk_chan".1'

Where “asterisk_chan” is the name of the extend_sh created in snmpd.conf file, and .1 on the end collates to the line of script output, .2 returns the second line and so on.

Add to monitoring

When adding to your monitoring system, in this example Zabbix, use the command listed in the testing phase to grab the values…

Logging and monitoring is now enabled for the Asterisk service…

Many of our PBX’s were deployed from the vendors ISO and so run atop of Gentoo, and it has a couple of issues:

1. We’ve been told not to “emerge” anything by the vendor, as the base OS on the image is not maintained.
2. Portage (Gentoo’s package manager) has fallen out of date, meaning even if emerge is attempted, it’ll fail as all repository links are broke.

If faced with the same issue, this is how to install net-snmpd from source, add it a startup service and be able to monitor via snmp…

Installation

On the Gentoo box, move to your home directory

cd ~

Download the source .tar.gz file

wget https://sourceforge.net/projects/net-snmp/files/net-snmp/5.9.4/net-snmp-5.9.4.tar.gz

Visit http://www.net-snmp.org/download.html for the latest version. When I was downloading SourceForge’s SSL cert had expired, if this happens add –no-check-certificate after wget in the command above.

Untar the file to your home directory, and change into it

tar -xzvf net-snmp-5.9.4.tar.gz
cd net-snmp-5.9.4

Run the configuration script

./configure

This allows you to set snmp version, file installation locations and snmp details, with exception of snmp version these can be left as default (Hit enter at the prompt). snmp details will look like this if left default…

Compile and install snmpd

make
make install

The make process is quite CPU intensive, may want to do this during a quiet period for the server.

Some libraries are not where they need to be, namely:
libnetsnmpagent.so.40
libnetsnmpmibs.so.40
libnetsnmp.so.40

Find where they were installed

find / -name libnetsnmpagent.so.40

Pick the result that is not in your current working folder (the install setup) and link it to /usr/lib

ln -s /usr/local/lib64/libnetsnmpagent.so.40 /usr/lib/

Repeat this process with the other two files

ln -s /usr/local/lib64/libnetsnmpmibs.so.40 /usr/lib/
ln -s /usr/local/lib64/libnetsnmp.so.40 /usr/lib/

Now can test to see if snmpd can run

snmpd -v

Configuration

Create a configuration file, the “snmpconf” command can be used but I found it easier to create from scratch

nano /usr/local/share/snmp/snmpd.conf

For my needs, only this line is needed

rocommunity {community} {ip address}

Save and exit the editor.

Testing

If you’d like to test your configuration, run snmpd

snmpd

Test on the snmp target machine, for quick results snmpwalk can be run

snmpwalk -c {community} -v 2c {ip address}

When run, snmpd automatically switches to a background process. To stop the process ID needs to be found and killed

ps aux | grep snmpd

Here the process ID (PID) is 5716, use this with the kill command

kill -9 {PID}

Add Service

Create the new service file

nano /etc/init.d/snmpd

Paste the following

#!/sbin/openrc-run
 
depend() {
    after modules
}
 
start() {
    ebegin "Starting snmpd"
    start-stop-daemon --background --start --exec /usr/local/sbin/snmpd --pidfile /var/run/snmpd.pid \
    -- -p /var/run/snmpd.pid -c /usr/local/share/snmp/snmpd.conf
    eend $?
}
 
stop() {
    ebegin "Stopping snmpd"
    start-stop-daemon --stop --exec /usr/local/sbin/snmpd \
    --pidfile /var/run/snmpd.pid
    eend $?
}
restart() {
    ebegin "Restarting snmpd"
    start-stop-daemon --stop --exec /usr/local/sbin/snmpd
    start-stop-daemon --background --start --exec /usr/local/sbin/snmpd --pidfile /var/run/snmpd.pid \
    -- -p /var/run/snmpd.pid -c /usr/local/share/snmp/snmpd.conf
    eend $?
}

Save and exit the text editor, then make the file executable

chmod +x /etc/init.d/snmpd

Start the service, and check its running

/etc/init.d/snmpd start

/etc/init.d/snmpd status

Finally, to make snmpd start with the system, run

rc-update add snmpd default

References

Help Creating init.d file

https://big-elephants.com/2013-01/writing-your-own-init-scripts/
https://tecadmin.net/startup-shutdown-script-on-gentoo/

Experienced issue where the process-id in the PID file was not matching the PID of process. With help of below found flag for snmpd to specify PID file, and match that to init.d

https://forums.gentoo.org/viewtopic-t-886230-start-0.html