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JNCIA-SEC and JNCIS-SEC lab 15 of 16

Troubleshooting policy NAT and VPN

Five tickets, five faults across two firewalls: a NAT typing slip, a forgotten block, a destination NAT policy on the wrong address, a VPN on the wrong interface and a one-way rule. Prove each from the evidence.

Run this lab

It needs Standard: its 6 nodes are set to 8 vCPU and 11,776 MB in total.

In your workspace: Shared, then JNCIA-SEC and JNCIS-SEC SRX security guided labs, then 15 - Troubleshooting policy NAT and VPN

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

Level
Advanced
Time
About 100 minutes
Nodes need
8 vCPU, 11,776 MB
Smallest plan
Standard

The scenario

It's Monday morning. A contractor "tidied up" Hartwell's firewalls over the weekend and took his notes with him. Five tickets have landed on your desk. Each one has one fault behind it, on one firewall. Find them from the evidence, make the smallest fix, and close the tickets.

DeviceInterfaceAddressNotes
ISPGi0/0 / Gi0/1198.51.100.1/30 / 203.0.113.1/30The internet between the sites
SRX-HQge-0/0/0198.51.100.2/30Zone untrust, default route to the ISP
SRX-HQge-0/0/110.10.10.1/24Zone trust, Poole LAN
HQ-PCeth010.10.10.10/24Gateway 10.10.10.1
SRX-BRge-0/0/0203.0.113.2/30Zone untrust, default route to the ISP
SRX-BRge-0/0/110.20.10.1/24Zone trust, Falmouth LAN
BR-PCeth010.20.10.10/24Gateway 10.20.10.1
INETeth0192.0.2.10/24A web server on the internet, gateway 192.0.2.1 (the ISP)
TicketWhoComplaint
1Poole staff"Ping to 192.0.2.10 fails. So does the web."
2Poole staff"Ping works now, but the web still fails."
3Customers"Falmouth's public stock page at http://203.0.113.2:8080/ doesn't load."
4Both sites"Nobody can reach the other site."
5Falmouth"Poole can see our stock server now, but we can't reach their file server."

What you’ll practise

  • Trace a first packet through route, policy and NAT
  • Use match-policies, flow sessions and NAT counters
  • Use filtered flow traceoptions and remove them afterwards
  • Separate VPN faults from policy faults
  • Fix the fault rather than the symptom

The tasks

  1. Work from the packet's point of view
  2. Tickets 1 and 2
  3. Ticket 3
  4. Tickets 4 and 5
  5. Tidy up

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 policy NAT and VPN6 nodes, 5 links. Every link is listed as text below the diagram.ISPSRX-HQSRX-BRHQ-PCBR-PCINETge-0/0/1eth0ge-0/0/1eth0ge-0/0/0Gi0/0ge-0/0/0Gi0/1Gi0/2eth0
6 nodes, with the interface names each link uses. On a narrow screen, scroll the diagram sideways.
Every link, as text
  • SRX-HQ ge-0/0/0 to ISP Gi0/0
  • SRX-BR ge-0/0/0 to ISP Gi0/1
  • SRX-HQ ge-0/0/1 to HQ-PC eth0
  • SRX-BR ge-0/0/1 to BR-PC eth0
  • ISP Gi0/2 to INET eth0
Nodes in Troubleshooting policy NAT and VPN, with the image each runs and the vCPU and RAM it’s set to
NodeDeviceImage in Add NodeSet to
ISPCisco IOSvvios-adventerprisek9-m.spa.159-3.m91 vCPU, 512 MB
SRX-HQJuniper vSRX NextGen templatevsrxng-24.4R1.92 vCPU, 4,096 MB
SRX-BRJuniper vSRX NextGen templatevsrxng-24.4R1.92 vCPU, 4,096 MB
HQ-PCEVE-NG GUI server (Docker)eve-gui-server:latest1 vCPU, 1,024 MB
BR-PCEVE-NG GUI server (Docker)eve-gui-server:latest1 vCPU, 1,024 MB
INETEVE-NG GUI server (Docker)eve-gui-server:latest1 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 JNCIA-SEC and JNCIS-SEC SRX security guided labs.

  3. Open 15 - Troubleshooting policy NAT and VPN 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.