Posted on March 1, 2011 by Zeeshan A Zakaria
Today I happened to troubleshoot a server in a remote part of the world, which I had shipped with SNMP and MRTG installed. It was a very wise decision to do this at that time, as it made an important troubleshooting very simple, which otherwise could have wasted days and still yielded no results.
While going over my notes in this regard, I thought to put this information here as well if it could help someone else who is looking to do a similar setup. But you should know that setting up SNMP can be tricky and the following might not work for you.
SNMP – Simple Network Monitoring Protocol, as it name suggests, is a protocol used to monitor various properties of network equipment. These properties are identified by something called OIDs (Object Identifiers) which are long numeric strings and identify various things, like hardware version, time on the device, data flow rate, and tons of other stuff. OIDs and grouped in what is called a MIB (Management Information Base). Asterisk has a list of its own OIDs which provide various pieces of information over the SNMP when requested by a software or hardware which is interested in that information. More on SNMP you can read on the Internet.
The following assumes that you do have SNMP module installed with your asterisk installation. You select this when running the #make menuselect just before the installation of asterisk. See my blog on asterisk installation for more details.
SNMP Setup
Following are the steps which I used on this CentOS 5.3/Asterisk 1.4 machine to setup SNMP:
1 yum install net-snmp-util
Created /etc/snmp/snmpd.conf with the following:
; Add this at the bottom
master agentx
agentXSocket /var/agentx/master
agentXPerms 0660 0550 nobody asterisk
; main configuration of the snmp
com2sec local localhost public
com2sec mynetwork 192.168.1.0/24 public
group notConfigGroup v1 notConfigUser
group notConfigGroup v2c notConfigUser
group MyROGroup v1 local
group MyROGroup v2c local
group MyROGroup v1 mynetwork
group MyROGroup v2c mynetwork
view all included .1 80
access MyROGroup "" any noauth exact all all none
Going into the detail of what all these lines mean is not the goal here, but the words in bold red are the ones which will be specific to your own network. The word ‘public’ is like a password, and almost all SNMP devices come preconfigured with this password. The user is ‘asterisk’, in your setup it might be ‘root’ or some other user.
Asterisk SNMP Config
Now add the following in /etc/asterisk/res_snmp.conf. If the file doesn’t exist, create one:
1 [general]
2 subagent = yes
3 enabled = yes
And now copy the Asterisk related MIB to the SNMP folder:
1 cp /usr/share/doc/asterisk-1.4.22/digium-mib.txt /usr/share/snmp/mibs
2 cp /usr/share/doc/asterisk-1.4.22/asterisk-mib.txt /usr/share/snmp/mibs
It is possible that these files don’t exist on your system, in which case you’ll have to get them from the Internet.
Next do the following:
1 export MIBS=+ASTERISK-MIB
2 chmod 755 /var/agentx
Done
This is all. Now restart asterisk, add snmpd and snmptrapd in chkconfig and start these services as daemons:
1 chkconfig snmpd on
2 chkconfig snmptrapd on
3 service snmpd start
4 service snmptrapd start
Testing it
In order to test if SNMP is properly installed, do the following:
1 snmpwalk -On -c public -v 2c localhost asterisk
and it’ll give you a list of the asterisk related MIBS
