Hierarchy rules for IP Subnetworks

These rules apply only when creating or updating an IP Subnetwork (which always has a parent — either an IP Address Block or another IP Subnetwork).

Rule	Whats checked	Rejected example	Error message
Subnetwork falls within parent	The subnetwork’s CIDR is a strict subset of the parent’s range.	Parent 20.0.0.0/24, child 30.0.0.0/24	"Invalid CIDR: The current CIDR ( 30.0.0.0/24 ) is not within the parent range ( 20.0.0.0/24 )"
Subnetwork more specific than parent	The subnetwork’s prefix is longer than the parent’s. The subnetwork can't be identical to the parent.	Parent 10.10.0.0/16, child 10.10.0.0/16	"IP Subnetwork cannot be identical to the Parent ( 10.10.0.0/16 )"
Unique under same parent	No other subnetwork under the same parent has the same CIDR.	Sibling 10.0.0.0/26 already exists under parent 10.0.0.0/20; new subnetwork attempts 10.0.0.0/26	"Subnet CIDR 10.0.0.0/26 already exists under the same Parent ( 10.0.0.0/20 )"

Overlap advisory

When a subnetwork’s CIDR overlaps with — but is not identical to — an existing sibling under the same parent, the system displays a warning but does not block the save. The user can acknowledge the warning and continue.

Warning text:

Subnet CIDR ( {new CIDR} ) overlaps with existing CIDR ( {existing CIDR} ) under the same Parent ( {parent CIDR} ). Do you want to continue ?

Uniqueness at top level — IP Address Blocks

The hierarchy rules above apply to IP Subnetworks. An IP Address Block is a top-level record without a parent block, and its uniqueness is scoped by Managed Network rather than by a parent.

If the IP Address Block has a Managed Network value, the CIDR must be unique within that Managed Network. The same CIDR may exist in different Managed Networks.
If the IP Address Block has no Managed Network, the CIDR must be unique across all IP Address Blocks that have no Managed Network.

Parent Topic:Telecommunications Network Inventory reference

Create an IP Subnetwork record

IP Subnetwork form

IP Address Block form