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FortiGate lab 18 of 25

Redundant IPsec VPN over two ISPs

Add a second tunnel over the second ISP, tune dead peer detection, use route distance so the backup takes over by itself, prove it by failing the primary ISP, and compare active-standby with active-active designs.

Run this lab

It needs Lite: its 5 nodes are set to 5 vCPU and 7,680 MB in total. That fits the free demo too.

In your workspace: Shared, then FortiGate NSE 4 guided labs, then 18 - Redundant IPsec VPN over two ISPs

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Level
Advanced
Time
About 60 minutes
Nodes need
5 vCPU, 7,680 MB
Smallest plan
Lite

The scenario

The tunnel you built in lab 17 now carries the branch's accounting system, and last week ISP-A was down for two hours. Both sites have a second internet line from ISP-B. Add a second tunnel over ISP-B that takes over by itself when ISP-A fails, and hands traffic back when it recovers. The primary tunnel (HQ-to-BR-A / BR-to-HQ-A) is already built and working.

DeviceInterfaceAddressConnects to
FGT-HQport1 / port3203.0.113.1/24 / 192.0.2.1/24ISP-A / ISP-B (gateways .254)
FGT-HQport210.1.10.1/24PC1 10.1.10.10
FGT-BRport1 / port3203.0.113.2/24 / 192.0.2.2/24ISP-A / ISP-B (gateways .254)
FGT-BRport210.2.10.1/24H2 10.2.10.50

Second tunnel (teaching values): HQ-to-BR-B / BR-to-HQ-B over ISP-B, IKEv2, pre-shared key LabVpnKey2!, des-sha256, DH group 14.

Evaluation licence. These FortiGates run with low-strength encryption only, so IPsec offers DES only (des-md5 to des-sha512): no AES, no 3DES. The lab uses des-sha256 with DH group 14 to get working tunnels. Never use DES in production: use AES-256-GCM (aes256gcm-prfsha384) with DH group 19, 20 or 21.

What you’ll practise

  • Build a second, independent tunnel over a second ISP
  • Tune dead peer detection so failures are noticed in seconds
  • Use route distance so a backup tunnel takes over automatically
  • Fail the primary path and watch routes and sessions move
  • Compare active-standby, active-active and SD-WAN overlays for redundant VPNs

The tasks

  1. Start the lab
  2. Check the primary tunnel and its DPD
  3. A second tunnel over ISP-B
  4. Routes and policies for the backup
  5. Fail ISP-A and watch the switch-over
  6. Choosing a redundancy design (reading task)

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 Redundant IPsec VPN over two ISPs5 nodes and 2 networks, 8 links. Every link is listed as text below the diagram.FGT-HQFGT-BRINETPC1H2ISP-AISP-Beth0eth1port1port3port2eth0port2eth0port1port3
5 nodes and 2 networks, with the interface names each link uses.
Every link, as text
  • FGT-HQ port1 to ISP-A (network)
  • FGT-BR port1 to ISP-A (network)
  • INET eth0 to ISP-A (network)
  • FGT-HQ port3 to ISP-B (network)
  • FGT-BR port3 to ISP-B (network)
  • INET eth1 to ISP-B (network)
  • FGT-HQ port2 to PC1 eth0
  • FGT-BR port2 to H2 eth0
Nodes in Redundant IPsec VPN over two ISPs, with the image each runs and the vCPU and RAM it’s set to
NodeDeviceImage in Add NodeSet to
FGT-HQFortinet FortiGatefortinet-FGT-v7.0.17.M-build06821 vCPU, 2,048 MB
FGT-BRFortinet FortiGatefortinet-FGT-v7.0.17.M-build06821 vCPU, 2,048 MB
INETEVE-NG GUI server (Docker)eve-gui-server:latest1 vCPU, 1,024 MB
PC1EVE-NG GUI server (Docker)eve-gui-server:latest1 vCPU, 2,048 MB
H2Alpine Linuxclbalpinebase-alpine-base-3-20-31 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 FortiGate NSE 4 guided labs.

  3. Open 18 - Redundant IPsec VPN over two ISPs 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 Fortinet. The lab follows exam topics and isn’t vendor training material; vendor names identify the exams and the images in the workspace.