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CCNA lab 25 of 46

DNS: name resolution and diagnosing record problems

Query A, AAAA, MX, NS and PTR records from a Linux client, make a router resolve names, then work three help-desk tickets caused by a wrong A record, a client with the wrong DNS server and a mail record that points at nothing.

Run this lab

It needs Lite: its 5 nodes are set to 5 vCPU and 4,608 MB in total. That fits the free demo too.

In your workspace: Shared, then CCNA 200-301 guided labs, then 25 - DNS - name resolution and diagnosing record problems

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 50 minutes
Nodes need
5 vCPU, 4,608 MB
Smallest plan
Lite

The scenario

At Corbridge Accountants (domain corp.lab), the router DNS1 acts as the office's internal DNS server, and R1 is the gateway that also hosts the web and mail servers (10.25.9.80 and 10.25.9.25). Three tickets are waiting:

  1. "The intranet page never loads, but the website is fine."
  2. "PC1 can't open anything by name. IP addresses work."
  3. "Outside companies say our email bounces."

You'll learn to query DNS properly from a Linux client (H1), make R1 resolve names, then fix all three tickets.

DeviceAddressRole
R1Gi0/0 10.25.1.1/24; Lo1 10.25.9.80 and 10.25.9.25gateway, web and mail servers
DNS110.25.1.53/24DNS server for corp.lab
H110.25.1.50/24 (you set it)Linux admin laptop
PC110.25.1.20/24, gateway 10.25.1.1user PC (ticket 2)

All four sit on switch S1.

What you’ll practise

  • Explain the DNS hierarchy, recursive and iterative queries, and the common record types
  • Query each record type with nslookup and read the answers
  • Configure an IOS router as a DNS client and as a small DNS server
  • Diagnose and fix wrong records and wrong client DNS settings
  • Explain CNAME and PTR records and how clients cache answers

The tasks

  1. Get the admin laptop ready
  2. Query each record type
  3. Make the router a DNS client
  4. Ticket 1: the intranet doesn't load
  5. Ticket 2: PC1 can't resolve anything
  6. Ticket 3: email bounces
  7. Understand CNAME, PTR and caching

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 DNS - name resolution and diagnosing record problems5 nodes, 4 links. Every link is listed as text below the diagram.DNS1R1S1H1PC1eth0Gi0/2eth0Gi0/3Gi0/0Gi0/0Gi0/0Gi0/1
5 nodes, with the interface names each link uses. On a narrow screen, scroll the diagram sideways.
Every link, as text
  • R1 Gi0/0 to S1 Gi0/0
  • DNS1 Gi0/0 to S1 Gi0/1
  • H1 eth0 to S1 Gi0/2
  • PC1 eth0 to S1 Gi0/3
Nodes in DNS: name resolution and diagnosing record problems, with the image each runs and the vCPU and RAM it’s set to
NodeDeviceImage in Add NodeSet to
DNS1Cisco IOSvvios-adventerprisek9-m.SPA.159-3.M61 vCPU, 1,024 MB
R1Cisco IOSvvios-adventerprisek9-m.SPA.159-3.M61 vCPU, 1,024 MB
S1Cisco IOSvL2viosl2-adventerprisek9-m.ssa.high_iron_202009291 vCPU, 1,024 MB
H1Alpine Linuxclbalpinebase-alpine-base-3-20-31 vCPU, 512 MB
PC1VPCS 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 CCNA 200-301 guided labs.

  3. Open 25 - DNS - name resolution and diagnosing record problems 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 Cisco. The lab follows exam topics and isn’t vendor training material; vendor names identify the exams and the images in the workspace.