Subnets

Purpose

• View every subnet and the network it attaches to.
• Create a subnet with a CIDR range and an optional default gateway.
• Attach a subnet to one VNet or VLAN (the mapping is 1-to-1).
• Edit or delete existing subnets.

Prerequisites

• Minimum permission to view: networking.subnets.read
• Permission to create: networking.subnets.create
• Permission to edit: networking.subnets.update
• Permission to delete: networking.subnets.delete
• A VNet or VLAN should exist to attach the subnet to (or create the subnet inline while creating the network).

View subnets

1. Open Networking → Subnets.
2. Review the columns: Name, CIDR, Network Type (VNet, VLAN, or Unassigned), Network, Default Gateway, Date Created, and Last Updated.
3. Select a subnet name to open its details.
4. Select the Network value, which is a clickable link, to jump to the attached network's details.
5. Expected result: the subnet's summary (name, CIDR, default gateway, network, and timestamps) and tags are displayed.

Create a subnet

1. Open Networking → Subnets, then select Create Subnet.
2. Enter a Name for the subnet.
3. Enter the CIDR (for example 10.10.1.0/24); it must be a valid network address.
4. Choose the Network Type (VNet or VLAN).
5. Select the network to attach to; only networks that do not already have a subnet are listed (1-to-1 mapping).
6. Optionally enter a Default Gateway within the CIDR range.
7. Optionally add a resource group and tags.
8. Select Save.
9. Expected result: the subnet is queued for creation and you return to the Subnets list.

Edit or delete a subnet

1. Open Networking → Subnets.
2. To edit, select a subnet name, choose Edit on the summary card, update the fields, and Save.
3. To delete, select one or more rows in the list and choose Delete, then confirm in the dialog.
4. Expected result: edits are queued for update, and deleted subnets are removed from the list.

Best Practices

• Use a valid network-address CIDR, not a host address.
• Keep the default gateway inside the subnet's CIDR range.
• Attach one subnet per network to preserve the 1-to-1 mapping.
• Create the subnet first, or create it inline while creating its VNet or VLAN.