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Arista EOS lab 18 of 20

SR-MPLS with TI-LFA and an SR-TE policy

Move a running core from LDP to segment routing without touching BGP, protect it with TI-LFA, watch the repair label stack on the wire during a real link failure, then steer one service down a non-default path with an SR-TE policy and BGP colour.

Run this lab

It needs Standard: its 6 nodes are set to 6 vCPU and 9,216 MB in total.

In your workspace: Shared, then Arista EOS guided labs, then 18 - SR-MPLS with TI-LFA and an SR-TE policy

Run it on Standard from £5 a day

The free demo can’t run it: it has 6 vCPU and 8 GB, and this lab’s nodes need 6 vCPU and 9,216 MB together. Every lab plan includes every guided lab.

Level
Advanced
Time
About 110 minutes
Nodes need
6 vCPU, 9,216 MB
Smallest plan
Standard

The scenario

Northwind's core runs IS-IS, LDP and a BGP-free design, and it works. The team now wants three things LDP can't give: no label protocol to run, fast repair around a failed link, and the ability to send one service down a path of their choosing. You'll move to SR-MPLS without touching BGP, turn on TI-LFA, break a link while traffic runs, and steer a video service through P2.

LinkAddresses
PE1 Et1 to P1 Et110.0.1.0 and 10.0.1.1 /31
PE1 Et2 to P2 Et110.0.2.0 and 10.0.2.1 /31
PE2 Et1 to P1 Et210.0.3.0 and 10.0.3.1 /31
PE2 Et2 to P2 Et210.0.4.0 and 10.0.4.1 /31
P1 Et3 to P2 Et310.0.5.0 and 10.0.5.1 /31
RouterLoopback0Node SID indexNode label
PE110.255.0.11900001
PE210.255.0.22900002
P110.255.0.1111900011
P210.255.0.1212900012

Metrics are already set: PE1 to P1 to PE2 costs 20. The P2 to PE2 link costs 50 and the P1 to P2 link costs 100, so P2's own best path to PE2 goes back through PE1. That's deliberate, and it makes task 5 interesting. Host LANs: h1 192.168.1.10/24 behind PE1 Et3, h2 192.168.2.10/24 behind PE2 Et3. PE2's Loopback100 10.200.2.1/32 is the video service, in BGP.

What this virtual router shows. The labels, the repair and the steering in this lab are real forwarding in vEOS's software data plane, and you'll capture them. The timing isn't: a software router's loss figures tell you the repair works, not how many milliseconds a hardware line card would take. Capture on the raw port vmnicet1, because labelled transit packets don't appear on et1.

What you’ll practise

  • Enable SR-MPLS in IS-IS and give each router a node SID in the default SRGB
  • Compare LDP and SR tunnels in the tunnel RIB and retire LDP
  • Enable TI-LFA and read a backup path that needs an adjacency SID
  • Fail a link under load and capture the repair label stack
  • Steer one prefix into an SR-TE policy with a BGP colour

The tasks

  1. Address the hosts and read the baseline
  2. Turn on segment routing beside LDP
  3. Retire LDP
  4. Enable TI-LFA and read the repair path
  5. Fail the link under load
  6. Steer the video service with an SR-TE policy

The Lab Tasks pane has the scenario, these tasks, the checks to run, hints and the full solution.

Topology and devices

The network as it opens in EVE-NG, drawn from the lab’s own canvas, and the image each node runs.

Topology of SR-MPLS with TI-LFA and an SR-TE policy6 nodes, 7 links. Every link is listed as text below the diagram.PE1P1P2PE2h1h2Ethernet3eth0Ethernet3eth0Ethernet1Ethernet1Ethernet2Ethernet1Ethernet1Ethernet2Ethernet2Ethernet2Ethernet3Ethernet3
6 nodes, with the interface names each link uses. On a narrow screen, scroll the diagram sideways.
Every link, as text
  • PE1 Ethernet1 to P1 Ethernet1
  • PE1 Ethernet2 to P2 Ethernet1
  • PE2 Ethernet1 to P1 Ethernet2
  • PE2 Ethernet2 to P2 Ethernet2
  • P1 Ethernet3 to P2 Ethernet3
  • PE1 Ethernet3 to h1 eth0
  • PE2 Ethernet3 to h2 eth0
Nodes in SR-MPLS with TI-LFA and an SR-TE policy, with the image each runs and the vCPU and RAM it’s set to
NodeDeviceImage in Add NodeSet to
PE1Arista vEOSveos-4.33.1.1F1 vCPU, 2,048 MB
P1Arista vEOSveos-4.33.1.1F1 vCPU, 2,048 MB
P2Arista vEOSveos-4.33.1.1F1 vCPU, 2,048 MB
PE2Arista vEOSveos-4.33.1.1F1 vCPU, 2,048 MB
h1Alpine Linuxclbalpinebase-alpine-base-3-20-31 vCPU, 512 MB
h2Alpine Linuxclbalpinebase-alpine-base-3-20-31 vCPU, 512 MB

How to open this lab

  1. Sign in to your workspace at lab.cloudlabbox.com.

  2. In File Manager, open Shared, then the folder Arista EOS guided labs.

  3. Open 18 - SR-MPLS with TI-LFA and an SR-TE policy and start its nodes, then open Lab Tasks for the scenario and the steps.

The lab is read-only. You can start the nodes and configure the devices, but changes to the topology can’t be saved. To change it, rebuild it in your own folder.

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CloudLabBox is independent of Arista Networks. The lab follows exam topics and isn’t vendor training material; vendor names identify the exams and the images in the workspace.