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Level 5
Level 5


This lab explores the Segment Routing (SR) Topology Independent Loop-Free Alternative (TI-LFA) functionality. During the demonstration, the protection of a traffic flow is examined hop by hop. Using this method, multiple types of TI-LFA repair paths are encountered.

TI-LFA not only protects SR-carried traffic, but it also protects plain IP traffic, only imposing an SR label stack when a failure occurs. TI-LFA protects LDP-carried traffic as well, but that is outside of the scope of this demonstration.

The demonstration illustrates that TI-LFA can protect traffic flows against link failures, but also against node failures and local Shared Risk Link Groups (SRLG) failures.

This demonstration requires familiarity with networking architecture and routing fundamentals.

Check it out here:


  • Scenario 1: Explore Topology
  • Scenario 2: Configure TI-LFA on XRVR-11 and Verify Protection
  • Scenario 3: Enable TI-LFA on XRVR-1 and Verify Protection
  • Scenario 4: Verify TI-LFA Protection on Unlabeled Traffic
  • Scenario 5: Enable TI-LFA on XRVR-2 and Verify Protection
  • Scenario 6: Enable TI-LFA on XRVR-3 and Verify Protection
  • Scenario 7: Enable TI-LFA Node Protection on XRVR-11
  • Scenario 8: Enable and Verify Local SRLG Protection on XRVR-3


  • Laptop
  • Cisco® AnyConnect®


  • Cisco IOS XRv 6.2.1
  • Cisco VIRL


  • Virtual environment for building network topologies
  • Simulation of networking components
  • Capable of running a range of virtual machines (VMs) running Cisco operating systems (IOS-XE, IOS Classic, IOS-XR, and NX-OS)
  • Support for third-party VMs
  • Capture and analyze network traffic at any node
  • Validate configurations prior to physical deployment
Segment Routing
  • Segment Routing (SR) enables a unified, end-to-end, policy-aware network architecture from servers in the data center, through the WAN, and up to the aggregation.
  • SR is designed for SDN because it seeks the proper balance between distributed intelligence, centralized optimization, and application-based policy creation.
  • Other benefits of SR are related to operational simplicity, better scale (the SR policy is in the packet), and better utilization of the installed infrastructure (lower capex).



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