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Arista EOS lab 17 of 20

MPLS and LDP with a BGP-free core

Switch on MPLS and LDP across an IS-IS core, read the label tables, run iBGP on the PEs only, and prove with LSP ping and a packet capture that P routers running no BGP forward customer traffic on labels alone.

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 17 - MPLS and LDP with a BGP-free core

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 80 minutes
Nodes need
6 vCPU, 9,216 MB
Smallest plan
Standard

The scenario

The IS-IS core is running. Northwind now wants the P routers out of the customer routing business: carry labels, keep small tables, know nothing about customer prefixes. You'll switch on MPLS and LDP, run BGP on the PEs only, and prove that P1 really forwards on labels. P1 is the working path; the links to P2 cost 30 at the PEs.

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

Loopbacks: PE1 10.255.0.1, PE2 10.255.0.2, P1 10.255.0.11, P2 10.255.0.12. Host LANs: h1 192.168.1.10/24 behind PE1 Et3, h2 192.168.2.10/24 behind PE2 Et3. BGP AS 65000 runs on PE1 and PE2 only.

What this virtual router shows. vEOS really does push, swap and pop labels in its software forwarder, so everything in this lab is live traffic, not just a table. Its timing isn't hardware timing. Two things to know: labelled transit packets appear on the raw port vmnicet1, not on et1, and no mpls ip under a single interface didn't stop labelled traffic when we tested it, so control labels with LDP's per-interface setting instead.

What you’ll practise

  • Enable MPLS globally and LDP on chosen interfaces
  • Read LDP neighbours, bindings and the LFIB, and spot penultimate hop popping
  • Resolve iBGP next hops through LDP tunnels so the P routers carry no BGP
  • Prove labelled forwarding with LSP ping, LSP traceroute and a capture on a P router
  • See what a break in the LDP path does to the service

The tasks

  1. Address the hosts and record the baseline
  2. Enable MPLS and LDP
  3. Read the label tables
  4. Run iBGP on the PEs only
  5. Prove it forwards on labels
  6. See a break in the LDP path

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 MPLS and LDP with a BGP-free core6 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 MPLS and LDP with a BGP-free core, 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 17 - MPLS and LDP with a BGP-free core 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.