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Network+ lab 26 of 27

Troubleshooting 3: network performance

The branch link is 'slow', and the users can't say more. You measure it properly with ping and iperf, separate latency, jitter, loss and throughput, find a forgotten traffic shaper on the router and a faulty provider circuit (a WAN emulator), fix both and prove it with a new baseline.

Run this lab

It needs Lite: its 5 nodes are set to 5 vCPU and 2,560 MB in total. That fits the free demo too.

In your workspace: Shared, then CompTIA Network Plus N10-009 guided labs, then 26 - Troubleshooting 3 - network performance

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Level
Advanced
Time
About 60 minutes
Nodes need
5 vCPU, 2,560 MB
Smallest plan
Lite

The scenario

Branch users say that "the network is slow": file copies to head office crawl, and the new softphones sound robotic. The WAN circuit between head office (R1) and the branch (R2) is contracted at 1 Mbps. (Scaled down for the lab: these virtual routers forward at most about 2 Mbps, so every rate here is a twentieth of a real branch circuit. The troubleshooting is the same at any speed.) Your job is to replace "slow" with numbers, find every cause, and prove the fix with a before-and-after baseline.

DeviceInterfaceAddressNotes
H1eth010.10.10.10/24HQ test host (iperf client)
R1Gi0/0 / Gi0/110.10.10.1/24 / 10.0.12.1/30HQ router
WANeth0 ↔ eth1bridge, no addressthe provider's circuit (a WAN emulator)
R2Gi0/1 / Gi0/010.0.12.2/30 / 10.20.20.1/24branch router
H2eth010.20.20.10/24branch test host (iperf server)

What you’ll practise

  • Measure latency, jitter, packet loss and throughput with ping and iperf
  • Explain how each of them affects voice, video and file transfers
  • Isolate where on a path the delay and loss are added
  • Find a bandwidth bottleneck caused by a traffic shaper
  • Record a baseline and compare after a fix

The tasks

  1. Prepare the circuit and the test hosts
  2. Measure the baseline
  3. Find where the delay is added
  4. Find the bandwidth bottleneck
  5. Deal with the provider's circuit
  6. Prove it with a new baseline

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 3 - network performance5 nodes, 4 links. Every link is listed as text below the diagram.R1WANR2H1H2eth0Gi0/0Gi0/0eth0Gi0/1eth0eth1Gi0/1
5 nodes, with the interface names each link uses. On a narrow screen, scroll the diagram sideways.
Every link, as text
  • H1 eth0 to R1 Gi0/0
  • R1 Gi0/1 to WAN eth0
  • WAN eth1 to R2 Gi0/1
  • R2 Gi0/0 to H2 eth0
Nodes in Troubleshooting 3: network performance, with the image each runs and the vCPU and RAM it’s set to
NodeDeviceImage in Add NodeSet to
R1Cisco IOSvvios-adventerprisek9-m.SPA.159-3.M61 vCPU, 512 MB
WANAlpine WAN emulatorclbalpinewanem-alpine-wanem-3-20-31 vCPU, 512 MB
R2Cisco IOSvvios-adventerprisek9-m.SPA.159-3.M61 vCPU, 512 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 CompTIA Network Plus N10-009 guided labs.

  3. Open 26 - Troubleshooting 3 - network performance 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 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.