Cisco Optical Network Planner Configuration Guide, Releases 26.x.x

Optical subnets and their role in networks

Updated: March 10, 2026

Want to summarize with AI?

Overview

Describes the functionality of optical subnets and their role in networks. Explains the benefits of this feature and how it contributes to efficient and robust network planning.

An optical subnet is a network structure that

consists of a collection of spans with defined properties,
is automatically created when a new network is set up in Cisco ONP, and
must exist in at least one instance for every network.

When a new network is created, Cisco ONP links an optical subnet to it, ensuring that each network has its own optical subnet for proper operation.

Create optical subnet

Use this procedure to create an optical subnet in Cisco ONP for Non-SSON, SSON, or NCS 1010 networks.

Note

Check the Current Subnet check box in the properties window below the network tree, to make the subnet you created as the current subnet. You cannot uncheck the Current Subnet check box.

Before you begin

Note

For NCS 1010 networks, both C-Band and L-Band optical subnets appear by default, from the Release 7.9.1. For C-Band and C+L Futuristic networks, the L-Band optical subnet contains no fiber links unless upgraded or configured with an L-Band edge.

Procedure

Open the required network (Non-SSON, SSON, or NCS 1010) in which you want to create a subnet.

Expand Subnet in the network tree panel.

Click the Ellipsis icon available next to the Optical Subnet, and select Create Optical Subnet.

In the Create Optical Subnet dialog box:


If you are creating optical subnet for...	Then...
non-SSON network	From the Cband Rules drop-down list, choose the C-band design rules for the new optical subnet, then click Save.
SSON network	From the Band Type drop-down list, choose either C-Band or L-Band. From the Spectral Density drop-down list, choose the spectral density for the new optical subnet that you want to create. The selected spectral density determines the value of Name, CBand Rules or LBand Rules, and Maximum Number of Channels that appear in the Create Optical Subnet dialog box. Click Save.
NCS1001, NCS 1010 and NCS1014 networks	From the Band Type drop-down list, choose either C-Band or L-Band. From the Spectral Density drop-down list, choose the spectral density for the new optical subnet that you want to create. From Release 5.2, the range of spectral density has increased from 30 to 100 units. The selected spectral density determines the value of Name, CBand Rules or LBand Rules, and Maximum Number of Channels that appear in the Create Optical Subnet dialog box. Click Save.

(Optional) After the new optical subnet is created:


If you want to...	Then...
select a new spectral density	select a new spectral density from the Spectral Density drop-down list in the properties window displayed under the network tree.
add a fiber to a subnet	add a fiber to a subnet from the Fiber links drop-down list in the properties window. The fiber now appears in the Fiber links field. When you select the optical subnet, its corresponding fiber is highlighted in the map.
add a fiber to a subnet from the network tree panel	Click the Ellipsis icon available in the right side of the required optical subnet and select Edit Fibers. In the Info dialog box, click OK. The user interface will freeze to allow fiber selection from the map. Select the required fiber and click the Done button appearing near the zoom icon. Note When a fiber is added to one of the subnets, it is automatically removed from the other subnets. Only one subnet rule is associated with each fiber.
enable Auto SD	select a new spectral density, and check the Auto checkbox in the properties window displayed under the network tree. Auto-SD automatically adjust the optimized spectral density based on the Circuit Card type selected for the subnet spans.

Cisco ONP creates the new optical subnet with your selected properties and places it under OpticalSubnet in the network tree panel.

Need help?

Open a support case

(Requires a Cisco Service Contract)

The documentation set for this product strives to use bias-free language. For the purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. Learn more about how Cisco is using Inclusive Language.