# Manage subnets

> Add subnets to IPAM by hand or from a CSV file, and find the networks on your devices that are not in your inventory yet.

Section: IPAM  
Source: https://www.itva.com/docs/ipam/manage-subnets  
Last updated: 2026-11-03

In this guide, you add subnets to IPAM one at a time or from a CSV file. You also use live data from your devices to find networks that are not in your inventory yet.

## Before you begin

- You have permission to manage subnets.
- To find missing networks, you have synced **Interface IP Entries** from your devices. See [Sync data from your devices](https://www.itva.com/docs/getting-started/sync-data-from-your-devices).

## Add a subnet

1. In the portal, go to **Inventory** > **Subnets**.
2. Select **New Subnet**.
3. In **Subnet**, enter the network in CIDR notation. For example, `10.20.0.0/24`.
4. In **Name**, enter a name for the subnet.
5. Optional: select a **Location** and **Tags**.
6. Optional: in **DHCP Server**, select the Windows Server that gives out addresses in this subnet. See [Sync DHCP leases](https://www.itva.com/docs/ipam/sync-dhcp-leases).
7. Select **Save**.

The network address must not have host bits set. For example, `10.20.0.0/24` is correct and `10.20.0.1/24` is not. You can add IPv4 and IPv6 subnets. Each CIDR can be in your organization only one time.

The **Device Scan Settings** and **Application Scan Settings** fields are for scans that find devices and TLS certificates in the subnet. They do not add IP addresses to IPAM. See [Scan your network for TLS certificates](https://www.itva.com/docs/pki-clm/scan-your-network-for-tls-certificates).

## Import subnets from a CSV file

1. Go to **Inventory** > **Subnets**.
2. Select **Bulk Import**.
3. Optional: next to **CSV Import Template**, download the template.
4. Make a CSV file with the columns `cidr` and `name`. Put one subnet on each row.
5. Select the CSV file.
6. Select **Save**.

`subnets.csv`

```
cidr,name
10.20.0.0/24,Office LAN
10.20.1.0/24,Office Wi-Fi
```

## How subnets nest

ITVA nests subnets for you. When you save a subnet, ITVA makes the smallest subnet that contains it into its parent. Subnets inside the new subnet move under it.

For example, `10.20.0.0/24` is in your inventory. You add `10.20.0.0/16`. ITVA moves `10.20.0.0/24` under `10.20.0.0/16`.

The **Subnets** page shows the subnets as a tree. Select a subnet's arrow to show or hide the subnets inside it. When you search, the page shows a flat list.

## Find networks that are missing from your inventory

This is automated data. ITVA reads the IP address and prefix of each interface on your devices, and finds the networks that they belong to. Then it compares those networks with the subnets in your inventory.

1. Go to **Tools** > **Data Enrichment** > **Subnets**.
2. Select **Missing**.
3. In **Minimum size**, select the smallest network to show. The default is /29. To show host addresses too, select **/32 (all, incl. hosts)**.
4. For the network that you want to add, select **Add**. The **New Subnet** form opens with the network already filled in.
5. Enter a **Name**.
6. Select **Save**.

The page shows three counts. **Discovered Subnets** is the number of networks on your device interfaces. **Matched** networks are in your inventory, and **Missing** networks are not. **Within Supernet** shows the missing networks that are inside a larger subnet in your inventory.

To see where a network comes from, select **Details** in its row. The dialog shows each device, interface, IP address, VRF, and VLAN that uses the network.

## Delete a subnet

Caution: When you delete a subnet, ITVA also deletes all IP allocations in it. Subnets inside it move up to the parent of the deleted subnet.

1. Go to **Inventory** > **Subnets**.
2. Open the subnet.
3. Select the delete button.
4. Confirm.

## Check that it worked

1. Go to **Inventory** > **Subnets**.
2. Make sure that the subnet shows in the list, under its parent if it has one.
3. Open the subnet.
4. Make sure that the **Name** and **CIDR** are correct.

The **ARP Entries** card on the subnet's page shows the ARP entries for IP addresses in the subnet. This is live data from your devices. The card is empty until you sync ARP entries. See [Sync ARP and MAC entries](https://www.itva.com/docs/ipam/sync-arp-and-mac-entries).