Visualization of Native SR Path

This section explains the following topics:

Overview

Objective

Visualize the actual path traffic flows physically through the topology map, even if traffic is on a native SR IGP path (not SR-policy) over inter-AS option C.

Challenge

Visualizing the native SR IGP path is often an operational challenge. Without access to a streamlined and simple to use interface, diagnosing and troubleshooting the native path requires you to repeatedly login to network devices without a solution to improve efficiency.

Solution

With the Path Query option, the objective is to visualize the native path using the traceroute SR-MPLS multipath command to get the actual paths between the source and the destination. With Cisco Crosswork Network Controller, a traceroute command runs on the source device for the destination TE-router ID and helps in retrieving the paths. By using native gRPC calls from the Crosswork server, you are able to get the paths from the device which assist in visualizing the native path through which the traffic flows. Since the traceroute command results in an operation that might take time to converge, Cisco Crosswork Network Controller provides an asynchronous user experience where you can send a request for such an operation and then be notified when the output is ready for inspection.

How Does it Work?

  • Create a new path query, defining the headend and endpoint devices to find the available Native SR IGP paths.

  • Visualize the available Native SR IGP paths as defined by the query on the topology map.

  • Inspect the available paths and review the Output, Nexthop, Source, Destination, and Hop Index information.

  • Create additional path queries as needed based on service type and instance and visualize the paths on the topology map.

  • Troubleshoot any failed path queries.

Scenario 11 –Troubleshooting paths between native SR paths over inter-AS Option C

Scenario Context

Visualization of the path traffic flows is not readily available without manual tasks from different sources. Once attaining traffic flow paths, the data is often out of date. Cisco Crosswork Network Controller supports the creation of Path Queries, which you define within the GUI. This allows visualization of actual SR IGP paths between the source destination on a topology map. Cisco Crosswork Network Controller provides an asynchronous user experience where the user is notified when results are ready for inspection. This facilitates rapid troubleshooting for issues with native traffic flows.

Assumptions and Prerequisites

  • The device should have IOS XR version 7.3.2.

  • The device should have gRPC (Remote Procedure Call) enabled. To check, run “show grpc” the in device and follow these steps:

    • For gRPC without a secure connection: If gRPC is showing as not enabled, enable gRPC using the following commands: configure terminal; grpc; no-tls.

    • For gRPC with a secure connection: Upload security certificates to Cisco Crosswork Network Controller in order to connect to the device using the following commands: configure terminal; grpc.

  • Cisco Crosswork Optimization Engine server should have the devices imported with gNMI (Network Management Interface) capability and gNMI connectivity for the devices.

    • Make sure the credential profiles include connectivity information for gNMI. Go to Device Management > Credential Profiles. The Credential Profiles screen appears. Select a profile to edit. On the Edit Profile Devices screen, click + Add Another. For Connectivity Type, select GNMI. Add the User Name, Password, and Confirm Password information. Click Save.

    • Devices should have gNMI capability enabled in Cisco Crosswork Network Controller while attaching the device. Go to Device Management > Network Devices. Select the device to edit. The Edit Device Details screen appears. From the required Capability list, select GNMI. Click Save.

    • Devices should have the gNMI connectivity information enabled. Go to Device Management > Network Devices. Select the device to edit. On the Edit Device Details screen, under Connectivity Details, click + Add Another. For Protocol, select GNMI and add the IP Address / Subnet Mask information. Type the Port information and for Encoding Type, select JSON. Click Save.

Workflow

Procedure

Step 1

Select Services & Traffic Engineering > Path Query. The Path Query dashboard appears.

Step 2

Click New Query. The New Path Query panel appears on the right with the mapped Device Groups panel on the left.

Step 3

Enter the device information in the required fields to find available Native SR IG Paths.

  1. Select the Headend device from the list. For this example, select P-Edge-A1.

  2. Select the Endpoint device from the list. For this example, select P-Edge-B2.

Step 4

Click Get Paths. The Running Query ID pop-up appears.

Note

 
Path queries may take a moment to complete. When the Running Query ID pop-up appears, you can also select View Past Queries to return to the Path Query Dashboard. If you already had path queries in the list, you can view existing details as the new query continues to run in the background, which is indicated by the blue Running icon in the Query State column. When the new query state turn green, completed, it can be viewed.

Step 5

Click View Results when it becomes available on the Running Query ID pop-up. The Path Details panel appears with corresponding Available Paths details while the defined topology map appears with the available Native SR IG Paths on the left.

Step 6

Click on the Available Paths options (for example, Path 0 and Path 1) to review Status details for Output, Nexthop, Source, Destination, and Hop Index information. When you select one of the available paths, the map will update with the corresponding Device Groups topology mapping of Path 0 and Path 1.

Note

 
Ensure that the Show Participating Only check box is selected in the top-right corner of the map.

Note

 
There are three likely status outcomes to a path query. The screen captures below are independent examples not directly associated with the scenario’s workflow:

  1. Non-Broken Path (path is complete): Path Status shows as Found with path hop details and overlay shown.

  2. Broken Path (Path is complete): Path Status shows as Broken with path hop details and overlay shown.

  3. Broken Path (Path is not complete): Path Status shows as Broken with path hop details partially shown (depending on gNMI output for traceroute – see Step 17 for troubleshooting details) and overlay details partially shown. An Error message will appear indicating that the devices and links are not available.

Step 7

Select Services & Traffic Engineering > Path Query to return to the Path Query Dashboard.

Step 8

Ensure that the new path Query State column shows as completed with a green icon. The new path in the table will also show a Query ID link, both the corresponding Headend and destination Endpoint, and the Available Paths column will show 2 for both paths.

If a query state is broken, see the last step in the workflow for troubleshooting details.

Step 9

As needed, click on the Query ID link or click and select View Details to again review the Path Details panel and map.

Step 10

Create additional path queries by selecting Services & Traffic Engineering > Path Query. The Path Query Dashboard appears where the previous path queries are listed by Query ID.

Note

 

Make sure to set the Automatically delete query older than every < X > option within the number of hours needed from the Path Query Dashboard. The maximum number of hours provided is 24.

Step 11

Click New Query. The New Path Query panel appears on the right with the mapped Device Groups panel on the left.

Step 12

For Select Service, select the Type from the list. In this example, select L2VPN-SERVICE.

By utilizing Select Service, when you later select the Headend and Endpoint, the options are conveniently identified according to the relevant VPN service type.

Step 13

For Select Service, select the Instance from the list. In this example, select L2VPN_NM_P2P-NATIVE-210.

The topology map will update to show the path between both servers. In this example, P-Edge-B2 and P-Edge-C3 are isolated on the map showing the logical path.

Step 14

Select the following from the list:

  1. Headend: P-Edge-B2.

  2. Endpoint: P-Edge-C3.

Step 15

Click Get Paths.

The Running Query ID pop-up appears.

Step 16

Click View Results when it becomes available. The Path Details panel appears with the corresponding Available Paths details, while the defined topology map appears with the available Native SR IG Paths on the left. This view shows the actual, physical hops between B2 and C3 that is carrying the traffic.

Step 17

To troubleshoot any Failed path queries appearing in the Path Query Dashboard’s Query State column, select the “I” icon for error details.

In this example, the gNMI protocol is missing from the Connectivity Details for a previous path query with the Headend P-BOTTOMLEFT device and the Endpoint P-BOTTOMRIGHT devices. To troubleshoot the failed path query, do the following:

  1. Select Device Management > Network Devices.

  2. Find the device by Host Name and select the check box.

  3. Click the Edit icon at the top of the table. The Edit Device Details pop-up appears.

  4. In this example, the Connectivity Details for Protocol is missing gNMI. Click + Add Another and type GNMI until it appears in the list. Select it.

  5. Enter the IP Address / Subnet Mask information and Port field information.

  6. Enter the Timeout field as 30.

  7. In the Endcoding Type list, type JSON until it appears in the list. Select it and click Save.

  8. Select Services & Traffic Engineering > Path Query. The Path Query Dashboard appears.

  9. Click New Query. The New Path Query panel appears.

  10. Select the following from the list:

    1. Headend device: P-BOTTOMLEFT.

    2. Endpoint device: P-BOTTOMRIGHT.

  11. Click Get Paths.The Running Query ID pop-up appears.

  12. Click View Results when it becomes available. The Path Details panel appears with corresponding Available Paths details, while the defined topology map appears with the available Native SR IG Paths on the left and is now in a Completed state.