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Check Point CCSE lab 5 of 10

VPN troubleshooting: vpn tu and IKE debug

The branch tunnel has never worked, and nobody knows why. Work up the stack with vpn tu, cpstat, SmartLog, the IKEv2 trace and IOS debugs. Each fix uncovers the next fault, and each fault leaves different evidence: authentication, phase 2, then traffic selectors twice over.

Run this lab

It needs Standard: its 6 nodes are set to 10 vCPU and 15,872 MB in total.

In your workspace: Shared, then Check Point CCSE guided labs, then 05 - VPN troubleshooting - vpn tu and IKE debug

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 10 vCPU and 15,872 MB together. Every lab plan includes every guided lab.

Level
Advanced
Time
About 100 minutes
Nodes need
10 vCPU, 15,872 MB
Smallest plan
Standard

The scenario

A contractor configured the tunnel to the branch office, then left. It has never carried a packet. The design hasn't changed:

SettingValue
HQ VPN domainHQ-LAN, 10.0.0.0/24
Branch VPN domain172.16.0.0/24
GatewaysHQ-GW 67.83.0.111, BRANCH 198.51.100.2
Communitystar Northgate-Branches
IKEIKEv2 only, AES-256, SHA-256, DH group 19
IPsecAES-256, SHA-256, PFS with group 19
Pre-shared keyNorthgate-Branch-VPN-26 (this copy is correct)

There are four separate faults. Each one hides the next, so don't change anything until you've seen the evidence for it. For each fault, note the symptom, the evidence, the fix, and the test that proves it.

What you’ll practise

  • Clear a tunnel fully on both ends, and explain what a half-cleared tunnel looks like
  • Turn on IKE debugging and read iked0.ikev2trace
  • Use SmartLog's Reject logs and reject_category to classify a failure
  • Tell an authentication failure from a phase 2 mismatch and a traffic selector mismatch
  • Read the traffic selectors a gateway proposes, and spot the effect of NAT on them

The tasks

  1. Your toolkit
  2. Collect the first evidence
  3. Read the IKE trace
  4. Fix the faults, one layer at a time
  5. Prove the repair

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 VPN troubleshooting - vpn tu and IKE debug6 nodes and 2 networks, 7 links. Every link is listed as text below the diagram.SMSHQ-GWISPBRANCHHQ-PCADMIN-PCHQ-LANInternetGi0/0eth0eth0eth1Gi0/1Gi0/0eth0eth0
6 nodes and 2 networks, with the interface names each link uses. On a narrow screen, scroll the diagram sideways.
Every link, as text
  • SMS eth0 to HQ-LAN (network)
  • HQ-GW eth0 to HQ-LAN (network)
  • HQ-GW eth1 to Internet (network)
  • HQ-PC eth0 to HQ-LAN (network)
  • ADMIN-PC eth0 to HQ-LAN (network)
  • ISP Gi0/0 to Internet (network)
  • ISP Gi0/1 to BRANCH Gi0/0
Nodes in VPN troubleshooting: vpn tu and IKE debug, with the image each runs and the vCPU and RAM it’s set to
NodeDeviceImage in Add NodeSet to
SMSCheck Point Security Management Servercpsms-R81.20-Licensed4 vCPU, 8,192 MB
HQ-GWCheck Point Security Gateway VE (cpsg template)cpsg-R81.20-Licensed2 vCPU, 4,096 MB
ISPCisco IOSvvios-adventerprisek9-m.SPA.159-3.M61 vCPU, 512 MB
BRANCHCisco IOSvvios-adventerprisek9-m.SPA.159-3.M61 vCPU, 512 MB
HQ-PCAlpine Linuxclbalpinebase-alpine-base-3-20-31 vCPU, 512 MB
ADMIN-PCEVE-NG Firefox browser (Docker)eve-firefox:latest1 vCPU, 2,048 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 Check Point CCSE guided labs.

  3. Open 05 - VPN troubleshooting - vpn tu and IKE debug 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 Check Point and Cisco. The lab follows exam topics and isn’t vendor training material; vendor names identify the exams and the images in the workspace.