We come across a lot of good tech deals and old obsolete yet still very usable electronic equipment and figured it’s time to start an ebay store and hopefully turn a profit. Plus we love flipping old computers too. Further more, our items won’t be limited to just tech/electronic stuff but will also include whatever we think is cool, in good condition and saleable.
That being said, we have decided to call our ebay store ‘Goodies & Tech’. Right now we have a couple of fresh refurbed Dell Optiplex gaming converted PC’s for sale to start. We’ll be adding more items soon.
The active and passive check concept can be a little confusing to understand, especially if you’re new to Zabbix. Here is how to quickly make sense of it and if you’re familiar with SNMP traps, we can use that as a reference point as well.
The distinction between active and passive monitoring in both SNMP and Zabbix revolves around where the data is generated from and how the communication flows between the monitoring system and the monitored devices. When the devices proactively send data, it aligns with active monitoring, and when the monitoring system actively queries the devices, it aligns with passive monitoring.
Think of SNMP Traps (if you’re already familiar that is)
SNMP Traps (Active) In SNMP traps, the SNMP agents (devices) generate and send unsolicited messages to the SNMP manager (monitoring system) when specific events occur. This is similar to Zabbix’s active monitoring, where the Zabbix agents (endpoints) actively send data to the Zabbix server (monitoring system) at regular intervals.
Regular SNMP (Passive): In regular SNMP, the SNMP manager (monitoring system) polls the SNMP agents (devices) for specific information by sending “GET” requests, and the agents respond with the requested data. This is more similar to Zabbix’s passive monitoring, where the Zabbix server (monitoring system) polls the Zabbix agents (endpoints) to retrieve data.
But Should I Use Active Or Passive Checks In Zabbix?
Of course there is no avoiding this question but like with most answers in IT, we land on the good ol, all to common answer ‘it depends’. FYI – Zabbix uses passive checks by default but here is a breakdown to help you make your decision. I personally believe the default passive checks work fine for most uses cases. However, the decision to use active or passive checks in Zabbix depends on your specific monitoring requirements and network environment. Each method has its advantages and considerations, so it’s essential to understand the differences to make an informed choice:
1. Passive Checks:
Pros:
Simplicity: Passive checks are easier to set up as they require the Zabbix server to have access to the Zabbix agents, and the agents only need to be running and reachable.
Network-Friendly: If you have firewalls or network restrictions, passive checks are often more feasible, as the Zabbix server initiates the communication.
Less Load on Agents: Passive checks put less load on the monitored hosts, as they only respond when queried by the server.
Cons:
Slightly Delayed Data: Passive checks rely on the Zabbix server to initiate data collection, so there might be a slight delay in data retrieval compared to active checks.
2. Active Checks:
Pros:
Real-Time Data: Active checks provide real-time data as the Zabbix agents proactively push data to the server at defined intervals.
Lower Server Load: Active checks can reduce the Zabbix server’s load as agents are responsible for pushing data, and the server doesn’t need to poll multiple agents.
Cons:
Complexity: Configuring active checks requires additional setup on both the Zabbix server and agent sides.
Network Configuration: Active checks may require network adjustments, and the Zabbix server needs to be able to reach the agents directly.
Considerations:
If you have a simple network setup and no network restrictions, passive checks might be the easier choice to implement.
If you need real-time data and have a more complex network or specific security considerations, active checks could be the preferred option.
Many Zabbix users opt for passive checks by default due to its simplicity and ease of configuration. However, some may switch to active checks for specific use cases that require real-time data or to reduce the server load.
Ultimately, the choice between active and passive checks should be based on your specific monitoring requirements, network architecture, and any potential security or performance concerns. It’s also worth considering testing both methods in a controlled environment to see which one fits your needs best before implementing them in production.
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In this example, we use a Cisco switch (SF300-24P) to send SNMP traps to our Zabbix server. We’ll install a zabbix_trap_receiver.pl (perl script) on Zabbix server in order to process the SNMP traps.
Enable SNMP Traps On Cisco Switch
enable
conf t
snmp-server enable traps
snmp-server host <zabbix server ip> version 2c <your community string>
exit
copy run start
You can verify your SNMP config with:
show snmp
Enable SNMP On Cisco Switch
enable
conf t
Use the below command if you wish to add a Read-Only community string:
snmp-server community public RO
(where “public” is the Read-only community string)
Use the below command if you wish to add a Read-Write community string:
snmp-server community private RW
(where “private” is the Read-write community string)
Exit the configuration mode and save the settings with ->
exit
write memory
Bonus SNMP Commands
Disable SNMP:
no snmp server
Check SNMP status:
show snmp server
Re-enable SNMP:
snmp server
Set Up Your Zabbix Server To Receive And Process SNMP Traps
Step 1 – Ensure Port 162 Is Open On Your Zabbix Server
If the Linux distro you’re running Zabbix on has port 162 blocked, you will need to open it as SNMP traps are typically sent on port 162.
For Ubuntu, Rspbian, Debian distros you can try this cmd to open port 162
iptables -A INPUT -p udp --dport 162 -J ACCEPT
sudo service iptables restart
If you can’t get the ports opened with those commands, ask ChatGPT
Step 2 – Enable And Configure SNMP Traps On Your Device
(using a Cisco switch in my case as outlined in the beginning of this blog)
Step 3 – Edit Zabbix Server Config
sudo vim /etc/zabbix/zabbix_server.conf
Comment out log file path like so: #SNMPTrapperFile=/var/log/snmptrap.log
Since we will be using the tmp path, you need to uncomment (remove the hashtag) ‘SNMPTrapperFile=/tmp/zabbix_traps.tmp’
Turn on SNMP Trapper by removing the hastag and changing 0 to 1 like so:
StartSNMPTrapper=1
Step 4 – Install zabbix_trap_receiver.pl File To /usr/bin
If you’re having trouble using the wget command to get the perl script, you can download the zabbix_trap_receiver.pl (perl script) directly from us here and we can get it on the server another way.
Recommend you stick the file on your desktop so you can conveniently copy it up to your Zabbix server in the next coming steps.
From windows cmd line and copy the file up to your Zabbix server with SCP:
Add these two lines to bottom of config file with your correct community string (change ‘public’ to your community string):
authCommunity execute <your community string>
perl do “/usr/bin/zabbix_trap_receiver.pl”;
Step 8 – Install libssnmp-perl
Perl is often missing in modern Linux distributions so we will need to install it with this command:
sudo apt-get install libsnmp-perl
Step 9 – Restart Zabbix Server & snmptrapd Services
sudo service zabbix-server restart
sudo service snmptrapd restart
sudo zabbix_server -R config_cache_reload
Step 10 – Add the host to Zabbix Frontend
Refer to video for details but basically, just add your switch with an SNMP template, generate an snmp trap (WR command on Cisco switch should generate one) and check the SNMP Trap (fallback) item of your device in Zabbix.
Note – You will add your device just like any normal SNMP monitored device with an SNMP template, you do not need to change the port to 162 (what the switch sends snmp traps out on) as the perl script and the Zabbix snmp Trap (fallback) item will handle the snmp trap processing for you. You just need to make sure port 162 is open on your Zabbix server.
