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JNCIP-ENT lab 18 of 19

Troubleshooting OSPF BGP and policy

A contractor has left a network with six independent faults across OSPF, BGP and policy. Work up from the IGP, find each cause with the right show command, and put the design back.

Run this lab

It needs Standard: its 5 nodes are set to 11 vCPU and 11,776 MB in total.

In your workspace: Shared, then JNCIP-ENT JN0-650 guided labs, then 18 - Troubleshooting OSPF BGP and policy

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 11 vCPU and 11,776 MB together. Every lab plan includes every guided lab.

Level
Advanced
Time
About 75 minutes
Nodes need
11 vCPU, 11,776 MB
Smallest plan
Standard

The scenario

A contractor made changes at Northmere over the weekend and then left. On Monday morning, the head office can't reach the internet. Nobody has a record of what changed. The design is the one you know: R1 and R2 are border routers with an ISP each, R3 is internal, and OSPF and iBGP run inside AS 64500.

The design says:

ItemShould be
OSPFEvery link in area 0, with R1, R2 and R3 fully adjacent
Head office LAN10.60.1.0/24 on R3, in OSPF
iBGPR1, R2 and R3 on loopbacks, and each border router sets itself as next hop for eBGP routes
eBGPR1 to ISP-A (AS 64501), R2 to ISP-B (AS 64502)
Advertised10.60.0.0/16 to both ISPs, and nothing else
203.0.113.0/24Leaves through ISP-B, at local preference 150, by contract
DeviceInterfaceAddress
R1ge-0/0/0, ge-0/0/1, ge-0/0/2, lo010.0.12.1/30, 198.18.1.1/30, 10.0.13.1/30, 10.255.0.1/32
R2ge-0/0/0, ge-0/0/1, ge-0/0/2, lo010.0.12.2/30, 198.18.2.1/30, 10.0.23.1/30, 10.255.0.2/32
R3Gi0/0, Gi0/1, Lo0, Lo1010.0.13.2/30, 10.0.23.2/30, 10.255.0.3/32, 10.60.1.1/24

There are six faults. They're independent, and each has one realistic cause. Work from the bottom up: don't look at BGP until OSPF is right. Don't read the solution until you've tried, because the skill here is the order of your questions.

What you’ll practise

  • Diagnose an OSPF adjacency that will not form
  • Work out why an aggregate is hidden
  • Read a BGP notification
  • Find an unresolved next hop
  • Find a chain order fault and a match type fault

The tasks

  1. OSPF neighbour missing
  2. A LAN that nobody knows about
  3. A session that won't come up
  4. Routes that exist but can't be used
  5. An export policy that advertises nothing
  6. A contract that isn't being honoured

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 OSPF BGP and policy5 nodes, 6 links. Every link is listed as text below the diagram.R1R2R3ISP-AISP-Bge-0/0/1Gi0/0ge-0/0/1Gi0/0ge-0/0/2Gi0/0ge-0/0/2Gi0/1ge-0/0/0ge-0/0/0Gi0/1Gi0/1
5 nodes, with the interface names each link uses.
Every link, as text
  • R1 ge-0/0/0 to R2 ge-0/0/0
  • R1 ge-0/0/1 to ISP-A Gi0/0
  • R2 ge-0/0/1 to ISP-B Gi0/0
  • R1 ge-0/0/2 to R3 Gi0/0
  • R2 ge-0/0/2 to R3 Gi0/1
  • ISP-A Gi0/1 to ISP-B Gi0/1
Nodes in Troubleshooting OSPF BGP and policy, with the image each runs and the vCPU and RAM it’s set to
NodeDeviceImage in Add NodeSet to
R1Juniper vJunos-routervjunosrouter-24.2R1-S2.54 vCPU, 5,120 MB
R2Juniper vJunos-routervjunosrouter-24.2R1-S2.54 vCPU, 5,120 MB
R3Cisco IOSvvios-adventerprisek9-m.spa.159-3.m91 vCPU, 512 MB
ISP-ACisco IOSvvios-adventerprisek9-m.spa.159-3.m91 vCPU, 512 MB
ISP-BCisco 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 JNCIP-ENT JN0-650 guided labs.

  3. Open 18 - Troubleshooting OSPF BGP and policy 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 and Juniper Networks. The lab follows exam topics and isn’t vendor training material; vendor names identify the exams and the images in the workspace.