An issue that frequently comes up for IT managers is the need to find only certain types of devices within a heterogeneous network that contains many types and manufacturers of networked devices. I recently worked with a customer that wanted to locate about a hundred Windows Servers from a network that contained several thousand devices.
One way to approach this task is to discover all the devices, then pick out the ones you are looking for, the old needle in the haystack routine. This approach is time consuming and error prone. A better method is to leverage the information available from devices that support the SNMP protocol, which includes most operating systems. SNMP includes an object library of OIDs (Object Identifiers) that are set up by each manufacturer. A Google search for "Windows OIDs" found this site which listed the OIDs to identify Microsoft Server Operating Systems.
As you can see (table below), the OIDs are built in a hierarchy so, if I could search my network for servers which contain the OIDs below for workstations, servers and domain controllers, I should find all my Windows Server boxes.
You can make the difficult task of finding and sorting networked devices much more manageable. I use dopplerVUE, a network management tool that simplifies the whole process and helps find the needle in the haystack faster and without issues.
dopplerVUE provides an OID include/exclude discovery feature that makes it easy to accomplish this task.
Here are some steps for using dopplerVUE to improve the network discovery process. To get started the server must have the SNMP agent service running and you need the credentials (called a community string) to enter in the SNMP service "security" tab. Most servers use "public" as a default and are case sensitive. SNMP service is usually turned off by default, so you'll need to restart the service when you are done making changes.
Once you have the servers set up, you should create a discovery job within dopplerVUE to find the Windows Servers. dopplerVUE provides a discovery wizard that guides you through the step by step process as follows:
Step 1: Select a discovery method appropriate to the task. Use an IP address range that provides the most control over your discovery results.
Step 2: Set an IP range that includes the Windows Servers you are looking for in your search. Be careful, the larger the range you select, the longer it will take to complete the discovery.
Step 3: Select SNMP protocol.
Step 4: Enter the community strings for the servers. Your admin can provide these and you can always use public which is set as default on most servers.
Pictured below is a tab marked "Show sysObjectID include/exclude options". You can click on the tab, expand the Window and then select "include". You can then enter the OIDs we found earlier.
Step 5: In the workstation column you'll want to select SNMP poller and then Host MIB if you want to collect information about processor utilization, memory usage and disk space.
Step 6: Optional: Enter a name and description for this discovery job.
Now you can click finish and go to the Inventory>Discovery Jobs tab to watch the progress of the task. The job will start automatically assuming your dopplerVUE discovery service is running and you had the "run now" checkbox selected in step 6. If not, click on the job and start it.
You can watch the progress in the job details section and keep an eye on your inventory tab to see if new devices are being found. When new devices are found, they should appear in the workstation classification. You can change classifications or create new ones easily by right clicking on the objects in the workstation classification list.
This technique works for any search where you can separate the devices by manufacturer. Since each manufacturer determines how they want to build their SNMP library, you'll need to understand how they created their hierarchy. Fortunately there is a lot of good information available on manufacturer websites to help you. Here is more information about SNMP support within Windows.
If you're looking to improve network discovery and automate IT tasks to save time, try dopplerVUE for free for 30 days.
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