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CCNP ENARSI lab 20 of 35

Troubleshooting BGP

Kingfisher's BGP edge (lab 16) is broken in six places after a change by a junior engineer. Use session states, notifications, logs and the BGP table to find every fault, including two that only appear once the others are fixed.

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 CCNP ENARSI 300-410 guided labs, then 20 - Troubleshooting BGP

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Level
Advanced
Time
About 80 minutes
Nodes need
5 vCPU, 2,560 MB
Smallest plan
Lite

The scenario

This is Kingfisher Logistics' network from lab 16, rebuilt by a junior engineer from memory after a router replacement. The design hasn't changed: AS 64500, iBGP full mesh between Loopback0 addresses with next-hop-self at both edges; eBGP to ISP-A (AS 65550) between R1's Loopback100 (203.0.113.250) and 198.51.100.4 with TTL 2 and MD5 key **Isp-Md5-Key; ISP-A sends two prefixes (default and 192.0.2.0/24) and R1 should accept up to 10; eBGP to the subsidiary (AS 65010) with 10/30 s timers; R3 originates 203.0.113.128/25**; private AS numbers removed towards ISP-A.

The tickets:

  1. "R3 and R2 have no BGP session."
  2. "Kingfisher has no Internet routes at all; the ISP session never comes up."
  3. "R3 can't reach the subsidiary's LAN 172.30.1.0/24, although R3 has the route."
  4. "The ISP says it doesn't receive our public services block 203.0.113.128/25."
  5. Expect at least one more problem to appear once the ISP session comes up.
DeviceInterfaceAddressNotes
R1Lo0 / Lo10010.255.0.1/32 / 203.0.113.250/32iBGP / ISP peering
R1Gi0/2203.0.113.1/30to ISP-A R4
R2Lo0 / Gi0/210.255.0.2/32 / 192.168.25.1/30iBGP / subsidiary R5
R3Lo0 / Lo110.255.0.3/32 / 203.0.113.129/25iBGP / public services
R4 (AS 65550)Lo0 / Lo1198.51.100.4/32 / 192.0.2.1/24ISP
R5 (AS 65010)Lo1172.30.1.1/24subsidiary

What you’ll practise

  • Read BGP states (Idle, Active, Established) and notification messages to locate session faults
  • Diagnose wrong AS numbers, missing multihop, MD5 mismatches and maximum-prefix shutdowns
  • Diagnose routes that are received but not valid or best (next hop) and routes that are never originated (network mask)
  • Restore a session after a maximum-prefix shutdown

The tasks

  1. Read the session states
  2. Fix the iBGP session (ticket 1)
  3. Bring up the ISP session (ticket 2)
  4. Fix the routes that don't work (tickets 3, 4 and 5)
  5. Prove it

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 BGP5 nodes, 5 links. Every link is listed as text below the diagram.R1R2R3R4R5Gi0/1Gi0/1Gi0/0Gi0/0Gi0/0Gi0/1Gi0/2Gi0/0Gi0/2Gi0/0
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 R3 Gi0/0
  • R2 Gi0/0 to R3 Gi0/1
  • R1 Gi0/1 to R2 Gi0/1
  • R1 Gi0/2 to R4 Gi0/0
  • R2 Gi0/2 to R5 Gi0/0
Nodes in Troubleshooting BGP, 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
R5Cisco 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 20 - Troubleshooting BGP 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.