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JNCIS-ENT lab 5 of 17

Spanning-tree protection

Defend the spanning tree you built: shut out a switch that someone plugs into a desk port, stop a rogue switch from becoming root, and keep an alternate port blocked when BPDUs stop arriving on a link that is still passing traffic.

Run this lab

It needs Standard: its 3 nodes are set to 12 vCPU and 15,360 MB in total.

In your workspace: Shared, then JNCIS-ENT JN0-352 guided labs, then 05 - Spanning-tree protection

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 12 vCPU and 15,360 MB together. Every lab plan includes every guided lab.

Level
Advanced
Time
About 60 minutes
Nodes need
12 vCPU, 15,360 MB
Smallest plan
Standard

The scenario

The warehouse spanning tree from the last lab is in place: CORE1 is root, CORE2 is the backup root, and ACCESS uses its uplink to CORE1. Three things have gone wrong at other sites, and you will protect this network against all of them:

  1. Someone plugged a cheap switch into a desk port, and its BPDUs changed the topology.
  2. A misconfigured switch with priority 0 became root and dragged traffic through a slow link.
  3. A faulty fibre stopped carrying BPDUs in one direction while still passing frames, so a blocked port opened and created a loop.

To play the rogue device, CORE2's spare port ge-0/0/2 is cabled to ACCESS's desk port ge-0/0/2. It starts disabled ("not plugged in yet").

What you’ll practise

  • Explain the threats that BPDU, root and loop protection address
  • Configure edge ports with BPDU protection and recover a port it disabled
  • Configure root protection on designated ports and read the root-prevented state
  • Configure loop protection and explain what happens without it when BPDUs stop

The tasks

  1. BPDU protection on edge ports
  2. Root protection
  3. Loop protection

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 Spanning-tree protection3 nodes, 4 links. Every link is listed as text below the diagram.CORE1CORE2ACCESSge-0/0/1ge-0/0/0ge-0/0/1ge-0/0/1ge-0/0/2ge-0/0/2ge-0/0/0ge-0/0/0
3 nodes, with the interface names each link uses. On a narrow screen, scroll the diagram sideways.
Every link, as text
  • CORE1 ge-0/0/0 to CORE2 ge-0/0/0
  • CORE1 ge-0/0/1 to ACCESS ge-0/0/0
  • CORE2 ge-0/0/1 to ACCESS ge-0/0/1
  • CORE2 ge-0/0/2 to ACCESS ge-0/0/2
Nodes in Spanning-tree protection, with the image each runs and the vCPU and RAM it’s set to
NodeDeviceImage in Add NodeSet to
CORE1Juniper vJunos-switchvjunosswitch-23.4R2-S2.14 vCPU, 5,120 MB
CORE2Juniper vJunos-switchvjunosswitch-23.4R2-S2.14 vCPU, 5,120 MB
ACCESSJuniper vJunos-switchvjunosswitch-23.4R2-S2.14 vCPU, 5,120 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 JNCIS-ENT JN0-352 guided labs.

  3. Open 05 - Spanning-tree protection 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 JNCIS-ENT labs

All JNCIS-ENT labs

Related labs in other courses

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