SNMP

Servers Alive supports SNMP (Simple Network Management Protocol) GETs, SETs, and Traps.  An SNMP GET is where a network management system, such as Servers Alive, polls a device and collects specific information.  An SNMP SET is where a network management system sends instructions and/or updates to a network device.  An SNMP Trap is an alarm or other notification sent be a device to a network management system.  GETs and SETs are a bit more complex, so for this example, I'm going to cover using Servers Alive to receive SNMP Traps from a network device.

To start, I've enabled SNMP functionality on a Sonicwall router on my network with the IP address of the XP Pro machine where I'm running Servers Alive.  As shown in Figure 5, I've configured the Sonicwall router to send SNMP updates to 192.168.3.156, the LAN IP of my XP Pro machine running Servers Alive. 

Notice the Get and Trap Community Name of “public.”. This is the key, or password, used for authenticating between network management systems and devices, which has to match on both the Trap device and in the Servers Alive configuration.  The key “public” is a common default for SNMP Trap configurations.

Figure 5: Enabling Sonicwall router SNMP

Next, I configured Servers Alive to receive SNMP traps.  Clicking the Setup button shown earlier in Figure 1, there is a menu to configure various Built-in servers in the Servers Alive software.  In Figure 6, I've enabled the SNMP trap receiver by clicking the check box and leaving the default values.

Figure 6: Enabling SNMP trap receiver

Further, I've selected the Trap Alerts setting from the left hand side of the above screen, then Add from the Trap Alerts menu, and input an email address to send the alerts, as shown in Figure 7.

Figure 7: SNMP Trap alert email

Servers Alive can be configured to send network alarm notifications via email, paging, SMS, even instant messaging.  I chose email for its simplicity, thus I also needed to configure SMTP settings so Servers Alive can send emails in the event an alarm occurs on my network. 

Verizon is my ISP, so I set up an email account via my user page on Verizon.net for Servers Alive, and entered my SMTP settings in the Setup > Alerts menu as displayed in Figure 8, below.  Notice on the left, under Primary, there is a choice called Advanced.  This is where a user name and password for email authentication is entered.

Figure 8: SMTP email settings

As long as my XP Pro server has access to the Internet, Servers Alive is now able to send an email when there is a failure of any of the configured Checks I have described, or if there is a received SNMP Trap.

The message in Figure 9 is from an email sent by Servers Alive, triggered by an SNMP Trap from my Sonicwall router, which I configured back in Figure 5.  Although the output is a bit cryptic, reading through to the end turns up the informative statement “Administrator login denied...”. Obviously, a failed login to my router triggered this Trap, which I did intentionally for this example.  In a production environment, this could mean a possible security violation.

Figure 9: SNMP Trap message

I've now configured Servers Alive to ping, check disk space, login, and collect SNMP traps from various network devices, as well as to send emails in the event of a network issue.  Servers Alive places a small oval icon in the bottom right tray of my XP Pro machine, which changes to a Red Stop Sign in the even of a network alarm. 

Clicking on that icon produces a nice live summary of all my network devices as shown in Figure 10 below.  Notice the pinged devices show a 100% Response, the NAS devices report their remaining disk space in GB, and the network devices Servers Alive is logging into show an “OK” Response.

Figure 10: Network device summary

I've just scratched the surface of a powerful (and free) tool that will run 24x7 and let me know instantly if there are issues in my network.  Even in its Free version, Servers Alive has a lot more capability than I've demonstrated here, but this is a good start. 

Follow these steps, and you'll see that network monitoring isn't just for large networks with 24x7 staffed NOCs (Network Operations Centers). It is something even a small network can implement!

Tags: Network monitoring,

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