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JNCIS-ENT lab 4 of 17

Spanning tree with STP and RSTP

Three switches in a triangle: a loop that only spanning tree keeps safe. You find the root bridge the protocol chose by itself, put the root where the design wants it, steer a port role with path cost, and time a failure with RSTP and with classic STP.

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 04 - Spanning tree with STP and RSTP

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

The scenario

Ashby Freight's warehouse network has two core switches and an access switch, cabled in a triangle so that any single link can fail. A triangle is a loop, and only spanning tree stops frames circling it for ever. RSTP is running with default settings, so the switches have chosen a root bridge by themselves. The design wants CORE1 as the root, CORE2 as the backup root, and ACCESS's uplink to CORE1 as the forwarding path.

Each switch has an IRB address in VLAN DATA (10.10.10.1, .2 and .3) for testing.

What you’ll practise

  • Explain why a switched loop needs spanning tree, and what BPDUs carry
  • Predict the root bridge from bridge IDs, and set bridge priorities
  • Identify root, designated, alternate and backup ports and the discarding, learning and forwarding states
  • Change the topology with interface cost
  • Configure STP and RSTP and compare their convergence after a failure

The tasks

  1. Why spanning tree, and what it decided
  2. Roles and states
  3. Put the root where the design wants it
  4. Path cost
  5. RSTP convergence
  6. The same failure with classic STP
  7. BPDUs on the wire

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 with STP and RSTP3 nodes, 3 links. Every link is listed as text below the diagram.CORE1CORE2ACCESSge-0/0/1ge-0/0/0ge-0/0/1ge-0/0/1ge-0/0/0ge-0/0/0
3 nodes, with the interface names each link uses.
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
Nodes in Spanning tree with STP and RSTP, 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 04 - Spanning tree with STP and RSTP 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 Juniper Networks. The lab follows exam topics and isn’t vendor training material; vendor names identify the exams and the images in the workspace.