Network Creation Policy

Dear JDisc users,

We frequently get feedback from our users that JDisc Discovery creates IP4 networks that don’t exist. So what’s the reason for that? The reason is that JDisc Discovery tries to determine all IP addresses and subnet masks for a device. The IP address, together with the subnet mask, defines the IP4 network which a device belongs to.

How do you determine the IP4 network? It is pretty simple. You convert an ip address to a binary value, and then you use a binary and with the subnet mask as a binary value. That’ll give you the network’s base (or first address). There are pretty nice subnet calculators on the net. For instance, refer to It works the same way with IPv6, but there are more bits for the IP addresses and masks.

So what is the actual issue? There is no issue when every device is properly configured (with its IP address and its proper subnet mask). However, in reality, we experienced many devices where the subnet mask is misconfigured. So let’s assume that your network has the address, and let’s further take that a device has a wrong subnet mask (e.g. The correct network has already been configured in our product, but as JDisc Discovery scans the device, it finds a new subnet mask and thus creates the network, which doesn’t exist in reality.

So what is the solution? The solution is that we added a new configuration that allows users to configure the desired behavior.

Network Creation Policy Option
Network Creation Policy Option

With the new Network Creation Policy option, users can define when to create new networks. There are three options:

  • Never:
    JDisc Discovery will not create any networks by itself. It will only use and assign devices to already existing and configured networks.
  • Trusted Device Types (this is the new default)
    JDisc Discovery creates net networks only when it is scanning trusted device types. Trusted device types are types that are typically properly configured (routers, switches, firewalls) so that JDisc Discovery can trust their configuration. When those devices have a wrong configuration, then you might have other network issues as well.
  • Always:
    This is the old behavior. Whenever we find a device with an IP and configured subnet mask, then we create the network if it doesn’t exist.

Furthermore, we have added a new context menu to the IP4- and IP6 network report to delete selected networks. This will not delete any devices from the database, but just unlink the IP address from the deleted network.

We really hope that this important change makes your life easier!

Best regards,

About The Author

Thomas Trenz
I own and manage JDisc and its network inventory and discovery products. Before I started JDisc, I worked quite a long time for Hewlett-Packard developing software for network assessments and inventory projects. Feel free to contact me on Linked-In or Xing.

Leave A Comment

The reCAPTCHA verification period has expired. Please reload the page.