How to Monitor a Service with SNMP
Monitoring windows services is crtical to maintaining a reliable computing infrastructure. IsItUp offers the Windows Service Monitor to insure that critical windows services are operational and to restart them if required. However, sometime it is not possible to use the Windows Service Montior because RPC connectivity is not accessible, required ports are blocked by an external source such as an ISP or an account with the required privileges is not available. Using SNMP monitoring has a number of advantages including using a single port which makes it firewall friendly. In addition, it has a low network overhead, a simple security model, and is easy to configure.
will detect an error when the service is either stopped, uninstalled, or exits
either normally or due to a fault. IsItUp
accomplishes this in the following way.
The Windows SNMP service keeps a unique OID variable for each running service. If the service exits for any reason, the Windows
SNMP service deletes the corresponding OID variable. Consequently, the actual error IsItUp detects
when your service is not running for any reason is “Variable does not exist”. It is also worthwhile to note that the
Windows SNMP service updates its OIDs slowly. The result of this is that it may be a minute
or more after a service has exited for the Windows
SNMP Service to delete the corresponding OID variable and thus for IsItUp to
detect your service has failed.
To quickly get started, first:
install IsItUp for a free 30 day trial.
Just click on the following link:
Once you have installed IsItUp, you
need to install and configure the Windows SNMP service on the target system. If you have already installed SNMP, please go
to step 9 to setup monitoring a service. The steps to install Windows SNMP are similar
for all versions of windows however, the following
screen shots are for Windows 7.
1. Select “Control Panel” from
the start menu.
2. Select “Programs” from the
Select the “Turn Windows features on or off” link from the control panel.
3. Check the “Simple Network
Management Protocol (SNMP)” checkbox on the Windows Features Dialog box.
4. Once Windows completes the
installation, you need to configure the service. Select the Start Menu and then enter “services.msc” in the search box and press return.
5. Select the SNMP services from
the list and double click.
6. Select the “General” tab and make
sure the service is set to “Automatic”.
7. Select the Security Tab and click
the “Add” button to set a “READ-ONLY” community string. Record this string as
you will need it when configuring IsItUp in Step 9. Then either select
the “Accept SNMP packets from any host” or “Accept SNMP packets from these
hosts” and specify the computer that IsItUp is running on.
8. Optional: If you need to change the default SNMP port,
open the windows “Services” file located at “C:\Windows\System32\drivers\etc\Services.” with any editor such as Notepad. You can change the port to anything you like
but the computer must be restarted for the change to take effect.
9. To create an IsItUp SNMP
Monitor, right click in the left most IsItUp Window (the device list window) and select “New Device / SNMP Monitor” from
the short cut menu.
10. In order to setup the monitor, you need to
fill in the name and group. You also
need the FQDN/IP address of the server you want to monitor as well as the Community
string you set in step 7. For additional
information on setup parameters, consult the IsItUp Help file. In order to determine the OID for the service
you want to monitor, you have two options.
You can compute the OID from the name of your service or you can use a
MIB browser to look it up.
In order to compute the OID, each character in the name of
the service you want to monitor is converted to a decimal ASCII number and
appended to 220.127.116.11.18.104.22.168.22.214.171.124 along with the number of characters in the
service name you want to monitor. For
example, there are 6 characters in IsItUp and consulting an ASCII table for the
character values, I=73,s=115,I=73,t=116,U=85,p=112. Putting
all that together, the OID for IsItUp is 126.96.36.199.188.8.131.52.184.108.40.206.220.127.116.11.116.85.112.
You can install one of the many freeware or open source MIB
browsers to lookup the OID. Then use the
MIB browser based on the products directions to locate your service’s OID. It is recommended that you load the LanMgr-MibII-MIB located at "C:\Windows\System32\lmmib2.mib"
into your MIB browser to make locating your services’ OID easier.
you determine the OID of your service, enter it in the OID field of the IsItUp
SNMP monitor. Select the “Octet” data
type. Then select the compare with
constant and set the comparison operator to “Contains”. Finally, set the constant value to the name
of your service. The following example
shows an IsItUp SNMP monitor setup to monitor IsItUp itself