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VXLAN EVPN lab 11 of 14

Troubleshooting the underlay

A rack move left three underlay faults behind: a BGP mismatch, a missing loopback and an MTU black hole. Find and fix them from the bottom up.

Run this lab

It needs Standard: its 7 nodes are set to 7 vCPU and 9,728 MB in total.

In your workspace: Shared, then VXLAN EVPN fabrics guided labs, then 11 - Troubleshooting the underlay

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 7 vCPU and 9,728 MB together. Every lab plan includes every guided lab.

Level
Advanced
Time
About 60 minutes
Nodes need
7 vCPU, 9,728 MB
Smallest plan
Standard

The scenario

A contractor finished the rack move at Calder Freight's Leeds data hall overnight and left this note: "fabric is up, BGP looks OK". The morning shift says otherwise. Hosts in VLAN 10 can't reach each other across racks, and after a first quick fix someone reports that small pings work but file transfers hang.

Everything is wrong in the underlay, not the overlay. The VNIs, RDs and route targets are all correct, so leave them alone. There are three faults. Work from the bottom up.

NodeASLoopbackFabric link
spine16500010.255.0.1Ethernet1–3 10.1.N.0/31
leaf1 (Cumulus)6500110.255.0.11swp1 10.1.1.1/31
leaf2 (Cumulus)6500210.255.0.12swp1 10.1.2.1/31
leaf3 (vEOS)6500310.255.0.13Ethernet1 10.1.3.1/31

Hosts h1 10.10.10.11, h2 10.10.10.12 and h3 10.10.10.13 are all in VLAN 10, VNI 10010.

What you’ll practise

  • Diagnose a failed eBGP session
  • Recognise an unreachable VTEP from invalid EVPN routes
  • Test for an MTU black hole with full-size pings

The tasks

  1. Start the lab
  2. Check every underlay session
  3. Check every VTEP is reachable
  4. Check there's room for the encapsulation

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 Troubleshooting the underlay7 nodes, 6 links. Every link is listed as text below the diagram.spine1leaf1leaf2leaf3h1h2h3Ethernet2swp1swp3eth0swp3eth0Ethernet3eth0Ethernet1swp1Ethernet3Ethernet1
7 nodes, with the interface names each link uses. On a narrow screen, scroll the diagram sideways.
Every link, as text
  • spine1 Ethernet1 to leaf1 swp1
  • spine1 Ethernet2 to leaf2 swp1
  • spine1 Ethernet3 to leaf3 Ethernet1
  • leaf1 swp3 to h1 eth0
  • leaf2 swp3 to h2 eth0
  • leaf3 Ethernet3 to h3 eth0
Nodes in Troubleshooting the underlay, with the image each runs and the vCPU and RAM it’s set to
NodeDeviceImage in Add NodeSet to
spine1Arista vEOSveos-4.33.1.1F1 vCPU, 2,048 MB
leaf1NVIDIA Cumulus VXcumulus-vx-5.9.11 vCPU, 2,048 MB
leaf2NVIDIA Cumulus VXcumulus-vx-5.9.11 vCPU, 2,048 MB
leaf3Arista 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
h3Alpine 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 VXLAN EVPN fabrics guided labs.

  3. Open 11 - Troubleshooting the underlay 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.

More VXLAN EVPN labs

All VXLAN EVPN labs

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