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CCNP ENARSI lab 7 of 35

OSPF virtual links, authentication and path preference

Reconnect an area that was added without touching the backbone, secure the backbone and the virtual link with MD5 and a transit area with HMAC-SHA-256, fix a cost problem caused by a 10 Gbps link, and compare E1 and E2 external routes.

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It needs Lite: its 4 nodes are set to 4 vCPU and 2,048 MB in total. That fits the free demo too.

In your workspace: Shared, then CCNP ENARSI 300-410 guided labs, then 07 - OSPF virtual links authentication and path preference

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Level
Advanced
Time
About 75 minutes
Nodes need
4 vCPU, 2,048 MB
Smallest plan
Lite

The scenario

Ashgrove University's network team added a research lab (area 2, router R4) last month by plugging it into the faculty router R3. R3 belongs to area 1, so area 2 never touched the backbone and the lab has been cut off from campus ever since. The security office also wants every backbone adjacency authenticated, the transit area protected with SHA-256, and the new 10 Gbps fibre between the core routers actually used. Finally, the research lab redistributes two external networks, and the team wants to understand why they show different metrics.

DeviceInterfaceAddressArea
R1Gi0/0 (10G) / Gi0/1 (1G)10.0.12.1/24 / 10.0.21.1/240
R1Lo110.1.1.1/24 (HQ LAN)0
R2Gi0/0 / Gi0/110.0.12.2/24 / 10.0.21.2/240
R2Gi0/210.0.23.2/241
R3Gi0/0 / Gi0/110.0.23.3/24 (area 1) / 10.0.34.3/24 (area 2)1 / 2
R4Gi0/0, Lo110.0.34.4/24, 10.4.4.1/24 (research LAN)2
R4Lo50 / Lo60192.168.50.1/24 / 192.168.60.1/24 (external)–
R*n*Lo010.255.0.n/32router's area

Topology: R1 =(two links)= R2 — R3 — R4. All links use the point-to-point network type.

What you’ll practise

  • Explain why every area must touch area 0 and repair a disconnected area with a virtual link
  • Configure area-wide MD5 authentication and understand why the virtual link needs it too
  • Configure OSPFv2 HMAC-SHA-256 authentication with a key chain
  • Correct link costs with auto-cost reference-bandwidth so a 10 Gbps link is preferred
  • Apply the OSPF path preference order: intra-area, inter-area, E1, E2

The tasks

  1. Find the disconnected area
  2. Repair it with a virtual link
  3. Authenticate area 0 with MD5, including the virtual link
  4. Protect the transit area with HMAC-SHA-256
  5. Make the 10 Gbps link count
  6. Compare E1 and E2 externals
  7. Test end to end

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 OSPF virtual links authentication and path preference4 nodes, 4 links. Every link is listed as text below the diagram.R1R2R3R4Gi0/1Gi0/0Gi0/0Gi0/0Gi0/1Gi0/1Gi0/2Gi0/0
4 nodes, with the interface names each link uses. On a narrow screen, scroll the diagram sideways.
Every link, as text
  • R1 Gi0/0 to R2 Gi0/0
  • R1 Gi0/1 to R2 Gi0/1
  • R2 Gi0/2 to R3 Gi0/0
  • R3 Gi0/1 to R4 Gi0/0
Nodes in OSPF virtual links, authentication and path preference, 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.m91 vCPU, 512 MB
R2Cisco IOSvvios-adventerprisek9-m.spa.159-3.m91 vCPU, 512 MB
R3Cisco IOSvvios-adventerprisek9-m.spa.159-3.m91 vCPU, 512 MB
R4Cisco IOSvvios-adventerprisek9-m.spa.159-3.m91 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 CCNP ENARSI 300-410 guided labs.

  3. Open 07 - OSPF virtual links authentication and path preference 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.