Cisco Crosswork Network Controller 7.2.x Administration Guide

Topology links

Updated: August 14, 2026

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Details the management and monitoring of network topology links within Crosswork Network Controller, covering link performance, L2 discovery protocols, and troubleshooting discovery issues in a network map.

A topology link is a network mapping element that

connects two devices within the network topology,
reports key properties such as link name, source and destination devices, status, bandwidth, and latency, and
provides real-time metrics, including utilization, traffic volume, and packet drops.

SR-PM delay and jitter metric availability

Delay and jitter metrics are available only when Segment Routing Performance Monitoring (SR-PM) is enabled. This comes with the Crosswork Network Controller Advantage package. For details on enabling SR-PM for links, refer to the Enable SR-PM Monitoring for Links and TE Policies section in the Cisco Crosswork Network Controller 7.2.x Service Health Monitoring guide.

View the link details

View comprehensive link details, including link name, state, type, endpoint interface, and aggregation within the topology. Refer the History tab that provides useful insights into the performance and trends of the network. You can select the time interval to analyze the data.

You can view the link details for each link. For more information on the link state, refer to Link states and discovery methods

Before you begin

LAG (Link Aggregation Group) discovery must be enabled to view LAG bundle members.

Procedure

	1.	From the main menu, choose Topology.
	2.	Select a link to view details. You can: Click a link directly on the topology map. In the Links tab within the topology map, click a specific link. In the Links tab on the Device details page, click a specific link. The link details pane displays link name, state, type, endpoint interfaces, and available history. Figure 1. Link details
	3.	Click a dashed line in the topology map to view aggregate link details. A dashed line represents an aggregated link that includes multiple physical links.
	4.	Review the interface details in the link details pane to view IPv4 unnumbered interface information, if available. IPv4 unnumbered interfaces information is displayed as a combination of the TE Router ID and the index.

Crosswork Network Controller displays detailed link information as you select each link, including link state, type, endpoints, aggregation, link history, and LAG member data if available.

What to do next

If you enabled LAG discovery, allow a few minutes for data collection to complete.

View link interface metrics

Access and interpret key performance indicators for a network link to assess communication quality and troubleshoot issues.

Review link interface metrics to monitor bandwidth, delay, jitter, and packet loss on communication links between network devices. These insights help optimize resources and plan for network upgrades.

Procedure

	1.	From the main menu, choose Topology.
	2.	Click a link on the topology map.
	3.	Expand either A side or Z side to display interface metrics. The utilization for IPv4 and IPv6 links shows total traffic and packet drops for the interface as a whole, not separately by address family. Combined values are reported for traffic metrics. Metrics may include bandwidth, delay, jitter, and packet loss. Figure 2. Link Interface Metrics

You can review comprehensive interface metrics to monitor link performance.

Link states and discovery methods

A link state and discovery method are network routing concepts that

enable routers to maintain an up-to-date map of the network topology,
allow routers to recognize and identify their neighbors using communication techniques such as static configuration, broadcast, multicast, or unicast, and
determine the operational status of network links (such as up, down, or degraded) to optimize routing decisions.

Link types, discovery and states

The table summarizes typical link types, discovery methods, and how link states are determined:

Table 1. Link Types, Discovery and States
Link type	Discovery method	Link state
L3 link (ISIS, OSPF and eBGP)	via SR-PCE	SR-PCE set it to UP or DOWN based on the link operational state When one direction of a link is operational while the other direction is down, then the link state is set as degraded.
L2 link (CDP, LLDP, LAG)	via SNMP MIB: CDP, LLDP and LAG	The link state is based on the two link endpoints operational states (via IF MIB). Link state is UP when initially discovered. When one of the endpoint interfaces is operationally down, then the link state is set to DOWN. When both endpoint interfaces are operationally up, then the link state is set to UP. When one direction of a link is operational while the other direction is down, then the link state is set as degraded.

IF-MIB data collection

Starting with the 7.2.x release, IF-MIB, interface-related inventory required for link discovery is collected through the Crosswork Network Controller inventory framework. Refer Crosswork Network Controller APIs to manage interface types for links discovery.

For details about interface inventory behavior and updates, see the Cisco Crosswork Network Controller 7.2.x Device Lifecycle Management.

Protocols for topology services

The table outlines the protocols and methods utilized to provide topology information, their key attributes, and typical use cases.


Protocol/Method	Provides	Use Cases
IGP/ BGP-LS (via SR-PCE)	Real time topology including nodes, links, link metrics and similar attributes	L3 topology visualization
PCEP (via SR-PCE)	Real time LSP status and CRUD of SR-PCE initiated LSPs	SR/SRv6, RSVP-TE LSP visualization SR-PCE initiated LSP create/update/delete actions
SNMP (SNMPv2-MIB, IP-MIB, IF-MIB, LLDP-MIB, (CISCO CDP-MIB) (via CDG)	System info,rmation, interface table (interface and SR-TE/RSVP-TE traffic Utilization) IP address tables and L2 adjacency information	Supports device management, provides device details, and enables model building for Crosswork Optimization Engine. L2/L3 topology Interface name, admin/oper status Interface and SR policy and RSVP-TE tunnel utilization
CLI (via CDG) - show mpls	TE router ID and so on.	Used to match the DLM node with the same TE router ID that is learned from the SR-PCE

Change L2 discovery settings

Control whether L2 (Layer 2) topology links using LLDP, CDP, and LAG protocols are visible on network maps.

L2 discovery allows the system to detect neighboring devices and their connections using LLDP, CDP, and LAG protocols. By default, this feature is disabled. When disabled, these topology links (including ones previously discovered) are hidden from maps. Enabling discovery makes protocol-based links visible.

Before you begin

Ensure all pods are healthy before changing L2 discovery settings.

Procedure

	1.	From the main menu, choose Administration > Settings > System Settings.
	2.	Under Topology, click the Discovery option.
	3.	Select or clear the checkboxes for the protocols you want to enable or disable.
	4.	Click Save.

The visibility of L2 topology links updates on network maps according to the protocols you selected.

What to do next

When you enable discovery, the system automatically creates the required collection jobs. For details about each collection job, see L2 discovery protocol collection jobs.

L2 discovery protocol collection jobs

When discovery is enabled, Crosswork Network Controller creates the required collection jobs for each L2 protocol. The table describes, for each supported protocol setting, the collection job IDs, context IDs, MIBs collected, and relevant sensor paths.

Table 2. Collection Jobs for each setting
L2 Configuration Setting	Helios collection Jobs ID	Context ID	MIBs collected	Sensor paths
None (default)	cw.topo_svc	`cw.toposvc.snmp` `cw. toposvc.snmptraps`	`IF-MIB, IP-MIB, LAG-MIB` IF-MIB:notification Note Starting with the 7.2.x release, `IF-MIB` data is collected using interface-related inventory through the Crosswork Network Controller inventory framework. Refer Crosswork Network Controller APIs to manage interface types for links discovery. For details about interface inventory behavior and updates, see the Cisco Crosswork Network Controller 7.2.x Device Lifecycle Management Guide.	`IP - MIB : IP-MIB / ipAddressTable / ipAddressEntry` `IF-MIB:notifications`
CDP	cw.topo_svc	`cw.toposvc.cdp`	`IF-MIB, CDP-MIB, LAG-MIB`	`CISCO - CDP - MIB : CISCO - CDP - MIB` `/ cdpCacheTable / cdpCacheEntry` `CISCO - CDP - MIB : CISCO - CDP - MIB / cdpInterfaceTable / cdpInterfaceEntry`
LLDP	`cw.topo_svc`	`cw.toposvc.lldp`	`IF-MIB, LLDP-MIB, LAG-MIB`	`LLDP - MIB : LLDP - MIB / lldpLocPortTable / lldpLocPortEntry` `LLDP - MIB : LLDP - MIB / lldpRemTable / lldpRemEntry`
LAG	cw.topo_svc	`cw.toposvc.lag`	`IF-MIB, LAG-MIB`	`IEEE8023 - LAG - MIB : IEEE8023 - LAG - MIB / dot3adAggTable / dot3adAggEntry` `IEEE8023 - LAG - MIB : IEEE8023 - LAG - MIB / dot3adAggPortTable / dot3adAggPortEntry`

Common errors for topology discovery settings

The table lists common errors that occur when enabling or disabling topology discovery, along with recommended actions to resolve each issue.

Table 3. Common error scenarios
Possible error scenario	Cause	Recommended action
After disabling, some of the disabled links are displayed in the maps.	A protocol that is disabled soon after being enabled may cause a problem. The system may stop the collection job for the previous enabled job before it finishes processing the SNMP data. This may lead to a mismatch between the actual and the displayed status of the links. The links that are disabled may still appear as enabled.	Enable and disable the protocol again with sufficient wait time in between, or restart robot-topo-svc. To restart the robot-topo-svc, refer to Monitor Platform Infrastructure and Application Health.
When you try to enable discovery, the helios job fails and settings are disabled from further editing.	A possible cause of the collection job being stuck in an unsuccessful state is that the helios pod is unhealthy. Crosswork prevents users from modifying the L2 discovery settings while the collection job is in progress. This means that the collection job cannot be canceled or restarted until the helios pod is healthy again.	Ensure that the pods are healthy, and then enable and disable the protocol with sufficient wait time in between,or restart robot-topo-svc. To restart the robot-topo-svc, refer to Monitor Platform Infrastructure and Application Health.
When you change the discovery settings, the topology UI or topology service crashes resulting in an unpredictable status.	The mechanism to disable users from further editing while the collection job is being created or deleted, relies on pods communicating via Postgres flag. If any pod crashes during this time, the Postgres flag key is not set correctly.

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