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Identifying Equal Cost Multiple-Paths

  1. Right-click on the topology map and select Labels > Link Labels > Show Link Metrics.
    Figure 1: Show Link DistanceDialog box titled Link Labels with options to display labels for links in a network diagram. Options include showing labels for all links, none, only current selection, add or remove current selection. Text options include interface name, utilization, IP subnet address, metric, delay, bandwidth, and customize. Includes OK and Cancel buttons.
  2. The link distances will be displayed and we can see that in this network, every metric has been set to 10. This is very likely to cause numerous equal cost multiple-paths to exist.
    Figure 2: Topology Map with Link DistancesNetwork topology diagram with nodes as icons signifying devices like routers or switches. Links labeled with 10 represent bandwidth or cost.
  3. Select Report > Report Manager to open up the Report Manager.
  4. Select Network Reports > Demand Reports > Equal Cost Multi-Path Report from the left panel to bring up the report listing all of the equal cost multiple-paths of the network. As can be seen in Figure 3, there are many such paths. This report is also saved on the server as EQPATHRPT. runcode. Note that the ECMP paths are calculated based on IP metric only, and do not factor in the influence of MPLS traffic engineering tunnels on the demand routing.
    Figure 3: Equal Cost Multiple-Paths ReportNetwork analysis tool interface showing ECMP routing report with metrics like FlowID, From_Node, To_Node, Bandwidth, and Path_Spec.
  5. Select Network > Path & Capacity > Equivalent Path to bring up the Demand Equivalent Path window.
    Figure 4: Network > Path & Capacity > Equivalent PathDropdown menu in a network management tool showing options like Link Rules, Path and Capacity, Equal Metrics at PE, and more.
  6. Select Node A and Node B, then click Show Path. The Path window will be displayed.
    Figure 5: Demand Equivalent PathGUI for Demand Equivalent Path tool showing dropdowns for Node A and Z, fields for IP addresses, owner, bandwidth, type, priority, and buttons for highlighting nodes and showing paths.
  7. All of the equivalent paths between the two selected nodes will be displayed in the Paths window. Select a path to view its detailed information and highlight it on the topology map.
    Figure 6: Equivalent Cost PathsNetwork visualization tool interface with two side-by-side panels. Top sections list network paths with names, interfaces, tunnel types, and node IDs. Bottom sections show network maps with nodes and color-coded links indicating utilization levels: red for high, yellow for moderate, and green/blue for low. The left and right panels compare different path configurations for network performance optimization.

    Reducing Equal Cost Multiple Paths

  8. If you choose your link metrics wisely (such as using the real distance in miles like in Figure 7), you can increase the variability of the path costs which will make it less likely for equal cost multiple-paths to occur.
    Figure 7: Topology Map With New Link DistancesNetwork diagram showing nodes connected by lines with numbers indicating link metrics like bandwidth and colors representing connection types.
    Figure 8: Routing according to Actual MileageConfiguration window for IP/MPLS network design showing path placement options. Includes max hop, routing method, placement order, path selection, peak rate, MPLS mode, max ECMP, frame size, and link balancing. Navigation menu on the left with sections for general, design, device, failure simulation, and report. Used by network engineers for simulating and optimizing networks.
  9. Open up the Equal Cost Multi-Path Report again and you will see that there are no longer any equal cost multiple-paths in the network with the new link metrics.
    Figure 9: New Equal Cost Multiple-Paths ReportSoftware interface showing a network report manager with a tree view of Layer 3 reports on the left and an ECMP info report on the right. Report metadata and table headers are visible.