Cisco Crosswork Planning Design 7.2.x User Guide

OSPF and IS-IS differences

Updated: August 14, 2026

Want to summarize with AI?

Describes the differences between OSPF and IS-IS routing protocol simulations.

OSPF and IS-IS simulations are identical with these exceptions:

OSPF routing uses OSPF areas, if specified. By default, all interfaces are assigned area zero.
IS-IS routing uses IS-IS levels, if specified. By default, all interfaces are set to Level 2. Interfaces can belong to Level 1, Level 2, or both. If both, then you can specify an alternate metric for Level 1.

OSPF area simulation

OSPF area membership can be specified per interface. The two interfaces on each circuit must belong to the same area. Area names can be any string. Area zero, the backbone area, must be denoted by ‘‘0’’, ‘‘0.0.0.0’’, or an empty string. Cisco Crosswork Planning simulates the OSPF area routing configuration in which the areas import Link State Advertisements (LSAs) from the backbone. A demand from a source node to a destination node in a different area will only be routed if it can reach the destination by passing through the source area, directly to area zero, and from there directly to the destination area.

By default, all nodes in a single AS are assumed to belong to a single OSPF area. This list describes how the nodes are assigned to areas:

If OSPF areas are not defined for interfaces, all nodes are assumed to be in the same area.
Each interface can be assigned to only one OSPF area. Note that each node can be assigned to one or more areas.
If a node has an interface in an OSPF area, the node is assigned to that area.
An Area Border Router (ABR) is a node that belongs to both area 0 and other OSPF areas.

Set OSPF area membership

Use this task to assign OSPF area membership to specific network interfaces.

Procedure

	1.	Open the plan file (refer to Open plan files). It opens in the Network Design page.
	2.	In the Network Summary panel on the right side, select one or more interfaces from the Interfaces table.
	3.	Click . Note If you are editing a single interface, you can also use the > Edit option under the Actions column.
	4.	Click the Advanced tab.
	5.	In the IGP panel, enter the required value in the OSPF area field.
	6.	Save the changes.

The OSPF area membership is configured for the selected interfaces.

IS-IS multi-level simulation

By default, IS-IS interfaces are assigned to Level 2, though you can assign them to Level 1 or to both Levels 1 and 2. For instructions, refer to Set IS-IS multi-level simulation.

The IGP metric defines the Level 1 metric for interfaces in Level 1, in Level 2, or in both Level 1 and 2 if these have equal metrics. However, you can change the Level 1 metric.
If an interface is in both Level 1 and Level 2 with uneven metrics, the IGP metric defines the Level 2 metric and the Level 1 metric defines the Level 1 metric.

The IS-IS level is listed in the ISIS level column of the Interfaces table, and the Level 1 metric is listed in the Metric ISIS level 1 column.

Node assignment rules

By default, all nodes in a single AS are assumed to belong to a single IS-IS level. This list describes how the nodes are assigned to levels:

Each node can be assigned to one or more levels.
Two Level 1 nodes are placed in different areas if any route between them (under normal operation) passes through a Level 2 node.
A node is assigned to a single Level 2 area if there is at least one interface that is Level 2, or both Level 1 and Level 2.
A node is assigned to one of potentially multiple Level 1 areas if any interface is Level 1, or both Level 1 and Level 2.
An ABR is a node belonging to both the Level 2 area and another IS-IS area.

Set IS-IS multi-level simulation

Use this task to configure IGP metrics, IS-IS levels, and Level 1 metrics for network interfaces in your plan file.

Procedure

	1.	Open the plan file (refer to Open plan files). It opens in the Network Design page.
	2.	In the Network Summary panel on the right side, select one or more interfaces from the Interfaces table.
	3.	Click . Note If you are editing a single interface, you can also use the > Edit option under the Actions column.
	4.	To set the IGP metric, enter its value in the IGP metric field.
	5.	To set IS-IS multi-level simulation, click the Advanced tab. In the IGP panel: Enter the IGP process ID. Select the level from the IS-IS level drop-down list. In the Level 1 metric field, enter the metric value.
	6.	Save the changes.

The IS-IS multi-level simulation is configured with the specified IGP metrics, IS-IS levels, and Level 1 metrics for the selected interfaces.

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.