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View Equal Cost Multiple-Paths

Equal Cost Multiple-Paths (ECMP) reports provide a list of all the ECMPs available in your network. You can also view each individual paths highlighted in a separate window.

To view ECMPs in your network:

  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 two sections: Show Labels for with options All, None, Only Current Selection, Add Current Selection, Remove Current Selection. What Text with options Interface Name, Utilization, IP Subnet Address, Metric selected, Delay, Bandwidth, Customize. OK and Cancel buttons at bottom.
  2. The link metrics are displayed.
    Figure 2: Topology Map with Link Distances Network topology diagram with nodes represented by icons for devices like routers or switches. Lines show connections with numbers indicating link costs or bandwidth.
  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 ReportScreenshot of Report Manager software showing a Layer 3 Network Report titled Equal Cost Multi-Path with ECMP details like flow ID, nodes, and bandwidth.
  5. Select Network > Path & Capacity > Equivalent Path to bring up the Demand Equivalent Path window.
    Figure 4: Network > Path & Capacity > Equivalent PathDropdown menu for network management software showing options like Link Rules, Path and Capacity, Equal Metrics at PE, Show Site Demands, Aggreg Demands, Aggreg Tunnels, Pricer, and Templates.
  6. Select Node A and Node B, then click Show Path. The Path window will be displayed.
    Figure 5: Demand Equivalent PathGraphical user interface for Demand Equivalent Path tool showing dropdowns for Node A and Node Z, IP and IPv6 fields, Bandwidth and Type inputs, and buttons for Highlight Nodes, Highlight All, Show Path, Close, and Help.
  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 path analysis interface showing two sections; top with tables of path details from ATL to BOS, and bottom with color-coded network maps indicating utilization levels.

    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 with nodes representing network devices connected by lines. Numbers indicate link metrics, and line colors denote connection types or priorities.
    Figure 8: Routing according to Actual MileageSoftware interface for configuring IP/MPLS network options under Design Path Placement with settings for Max Hop, Routing Method, Placement Order, Path Selection Method, MPLS-Enabled Mode, and buttons for OK, Cancel, Help.
  9. Open 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 Report Report Manager interface displaying report titled EQUAL COST MULTI-PATH INFO mpls-fish with network path details.