Discovery and MID Server example

The MID Server is very adept at ferreting out information, but it's up to you to give it the tools it needs to do the job.

Here's a simple scenario, stepped out to make it easy to follow. Your ServiceNow instance is running, and Discovery is enabled. You also have a MID Server somewhere in your network that you think is communicating with your instance. We'll do a Discovery on a single device.

MID Server Preparation

  • The first thing we do is to make sure the MID Server is started and connected to the instance.
  • We must configure our Discovery IP address ranges to include the address of the single device.

    In this case the device has an IP address of 10.10.10.5.

  • We must remember to specify credentials for the MID Server to use to log in to the device.

    Now that we've configured all the basics, we're ready to kick off a Discovery on 10.10.10.5.

  • To enable Discovery manually, click the Discover Now link in a Discovery Schedule record.

Discovery Happens

Once Discovery has started, it's all up to the MID Server.
  1. The instance prepares a probe for the MID Server with a range of IP addresses to test, and then delivers the probe when the MID Server checks in for jobs to do.
  2. The MID Server visits 10.10.10.5 (knocking on the device's door) and scans the ports.

    The port scan sees that the machine is listening on port 22, which means that this must be a UNIX or Linux machine.

  3. The MID Server advises the instance of what it has discovered.
  4. The sensor creates the Get Operating System probe and delivers it when the MID Server checks in for jobs again.
  5. The MID server probes the Linux machine to determine its operating system.
  6. When the machine replies Linux, the MID Server passes this information to the sensor.
  7. Because this is a Linux machine, the sensor asks the MID Server to send a few more probes to get information about the hard disk, the network adapters, and any processes that are running.
  8. The MID Server runs each of those probes and sends the results back to the sensor, which translates the findings for the instance.

Have We Met?

So now you have a list of devices that you found and a lot of information about those devices, but what can you do with this information? Chances are, you already know about many of the devices that Discovery finds in your network. Most of the computers, routers, printers, and so forth that you have in your Configuration Management Database (CMDB) will show up every time you run Discovery. Then there are those devices that you don't know about yet - devices recently added to the network perhaps - that are not in your CMDB. Well, it makes sense that you should add those new devices to your database, and it also makes sense to update existing devices, particularly if someone has installed new memory, new software, or added a disk drive. Discovery can do these things automatically.

Discovery can launch probes that return identity data from the devices it finds. Discovery then feeds that information into a handy tool called an Identifier that searches the CMDB for a matching device. If the Identifier determines that ServiceNow already has a record of the device, the Identifier can tell Discovery to launch more probes and update the existing record. If the Identifier cannot find a matching device in the database, it can tell Discovery to continue exploring and then create a new record in the database. If you don't want these automatic updates for any reason, you can tell the Identifier to stop Discovery and not change anything in the CMDB.

And that's all there is to it! We've learned how to Discover a device by using lightweight, remote probes, and we've learned that we can use the information returned to update our Configuration Management Database automatically.