CloudLabBox
Try the free demo

Network+ lab 7 of 27

Spanning tree: choosing the root and protecting edge ports

Three switches in a triangle give redundancy and a loop. You find out why the wrong switch became root, move to Rapid PVST+, place the root per VLAN so both uplinks carry traffic, protect edge ports with PortFast and BPDU guard, and watch a port go err-disabled.

Run this lab

It needs Lite: its 5 nodes are set to 5 vCPU and 4,352 MB in total. That fits the free demo too.

In your workspace: Shared, then CompTIA Network Plus N10-009 guided labs, then 07 - Spanning tree - choosing the root and protecting edge ports

Try it free for 30 minutesRun it on Lite from £3 a day

The free demo needs no card and no email. Every lab plan includes every guided lab.

Level
Intermediate
Time
About 55 minutes
Nodes need
5 vCPU, 4,352 MB
Smallest plan
Lite

The scenario

Harbour Logistics added a third switch, SW3, and cabled it to both core switches for redundancy. Since then users report slow transfers, and the network team noticed that traffic between the core switches takes a detour through SW3. Your job: find out why, put the spanning tree where the design says it belongs, and protect the user ports.

LinkSW endSW endCarries
Core linkSW1 Gi0/0SW2 Gi0/0trunk 10, 20
Uplink ASW1 Gi0/1SW3 Gi0/0trunk 10, 20
Uplink BSW2 Gi0/1SW3 Gi0/1trunk 10, 20
PC1SW2 Gi0/2-VLAN 10 (10.10.10.11)
PC2SW3 Gi0/2-VLAN 10 (10.10.10.12)

Design: SW1 is the root for VLAN 10 (priority 4096) and the backup for VLAN 20 (8192). SW2 is the root for VLAN 20 (4096) and the backup for VLAN 10 (8192). SW3 keeps the default priority.

What you’ll practise

  • Explain how STP prevents loops and how the root bridge is elected
  • Read root, designated and alternate port roles and port states
  • Set bridge priorities per VLAN to choose the root and load-balance
  • Switch to Rapid PVST+ and test failover
  • Configure PortFast and BPDU guard, and recover an err-disabled port

The tasks

  1. Find the root bridge and the blocked port
  2. Move to Rapid PVST+
  3. Put the root where the design says
  4. Test failover
  5. Protect the edge ports, and see BPDU guard trip

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 - choosing the root and protecting edge ports5 nodes, 5 links. Every link is listed as text below the diagram.SW1SW2SW3PC1PC2Gi0/2eth0Gi0/2eth0Gi0/0Gi0/0Gi0/1Gi0/0Gi0/1Gi0/1
5 nodes, with the interface names each link uses. On a narrow screen, scroll the diagram sideways.
Every link, as text
  • SW1 Gi0/0 to SW2 Gi0/0
  • SW1 Gi0/1 to SW3 Gi0/0
  • SW2 Gi0/1 to SW3 Gi0/1
  • SW2 Gi0/2 to PC1 eth0
  • SW3 Gi0/2 to PC2 eth0
Nodes in Spanning tree: choosing the root and protecting edge ports, with the image each runs and the vCPU and RAM it’s set to
NodeDeviceImage in Add NodeSet to
SW1Cisco IOSvL2viosl2-adventerprisek9-m.ssa.high_iron_202009291 vCPU, 768 MB
SW2Cisco IOSvL2viosl2-adventerprisek9-m.ssa.high_iron_202009291 vCPU, 768 MB
SW3Cisco IOSvL2viosl2-adventerprisek9-m.ssa.high_iron_202009291 vCPU, 768 MB
PC1VPCS hostBuilt in to EVE-NGCounted as 1 vCPU, 1,024 MB
PC2VPCS hostBuilt in to EVE-NGCounted as 1 vCPU, 1,024 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 CompTIA Network Plus N10-009 guided labs.

  3. Open 07 - Spanning tree - choosing the root and protecting edge ports 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 Network+ labs

All Network+ labs

Related labs in other courses

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