Default IPsec route configuration between Teltonika and Fortigate devices

The information in this page is updated in accordance with 00.07.07.2 firmware version.

Introduction

Normally we configure IPsec for LAN-to-LAN communication, also known as split-tunnel VPN, when only specific hosts should be reachable via a VPN tunnel. However, we may also take a different approach and configure a VPN tunnel using the full tunnel method. This means that any non-directly connected network (i.e. lan interface) will be reachable only via IPsec tunnel and not via the typical default route.

Configuration overview and prerequisites

Before we begin, let's look at the configuration we are attempting to achieve and the prerequisites that make it possible.

Prerequisites:

• One RUT/RUTX series router or TRB gateway with RUTOS firmware;
• One Fortinet series router;
• An end device (PC, Laptop) for configuration;

If you're having trouble finding this page or some of the parameters described here on your device's WebUI, you should turn on "Advanced WebUI" mode. You can do that by clicking the "Advanced" button, located at the top of the WebUI.

Topology

Fortinet – The Fortinet will act as a "default gateway" for the RUT device. Fortinet has a LAN subnet of 192.168.5.0/24 and WAN subnet of 192.168.10.2/24 configured on it, which should be reachable by the RUT.

RUT – The RUTX11 in this case will be connected to Fortinet for basic internet access. RUT has a LAN subnet of 192.168.1.0/24 and WAN subnet of 192.168.10.1/24 configured on it.

Fortinet configuration

Start by configuring the Fortinet device. Login to the WebUI, navigate to VPN → IPsec Tunnels → Create new → IPsec Tunnel → Template Custom. Configure everything as follows.

Note: Not specified fields can be left as is or changed according to your needs.

Network configuration

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Make the following changes:

1. Remote Gateway – Static IP Address;
2. IP Address – 192.168.10.1;
3. Interface – wan1;

Authentication configuration

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Make the following changes:

1. Method – Pre-shared Key;
2. Pre-shared Key – your desired password;
3. Version – 2;

Phase 1 Proposal configuration

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Make the following changes:

1. Encryption – AES256;
2. Authentication - SHA512;
3. Diffie-Hellman Group – 16;
4. Key Lifetime (seconds) – 86400;

Phase 2 Selectors configuration

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Make the following changes: Click on Advanced settings;

1. Encryption – AES256;
2. Authentication - SHA512;
3. Diffie-Hellman Group – 16;
4. Key Lifetime – Seconds;
5. Seconds – 86400;

Firewall configuration

After setting up our IPsec instance, we will need to configure our firewall accordingly. Navigate to Policy & Objects → Firewall Policy → and click on a Create new button.. Configure everything as follows.

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Make the following changes:

1. Incoming interface - Tunnel interface name (In this case it is Teltonika);
2. Outgoing interface - wan2 (choose WAN port from which Fortinet gets internet);
3. Source - 192.168.1.0/255.255.255.0;
4. Destination - all;
5. Service - ALL;

Static Routes configuration

After setting up our IPsec instance and firewall, we will need to configure our static route accordingly. Navigate to Network → Static routes → and click on a Create new button.. For that we will need to create two static routes, one for blackhole and one for accessing our RUT device, configure everything as follows.

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Make the following changes:

Destination - 192.168.1.0/255.255.255.0; Interface - Tunnel interface name (In this case it is Teltonika);

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Then create a new static route for blackhole. Make the following changes:

Destination - 192.168.1.0/255.255.255.0; Interface - Blackhole; Administrative distance - 254;

RUT configuration

Start by configuring the RUT device. Login to the WebUI, navigate to Services → VPN → IPsec and add a new IPsec instance. Configure everything as follows. Note: Not specified fields can be left as is or changed according to your needs.

Instance configuration

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Make the following changes:

1. Enable instance;
2. Remote endpoint - Fortinet WAN IP;
3. Authentication method - Pre-shared key;
4. Pre-shared key - the same password you have set on Fortinet when configuring the Fortinet IPsec instance;
5. Local identifier – RUT WAN IP;
6. Remote identifier – Fortinet WAN IP;

Connection general section configuration

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Make the following changes:

1. Mode - Start;
2. Type - Tunnel;
3. Local subnet – 192.168.1.0/24;
4. Remote subnet – 0.0.0.0/0;
5. Key exchange - IKEv2;

Connection advanced section configuration

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Make the following changes:

1. Enable local firewall
2. Remote DNS – 8.8.8.8;
3. Passthrough subnets – 192.168.1.0/24;

Proposal configuration

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Make the following changes:

Encryption - AES256; Authentication - SHA512; DH group - MODP4096; IKE lifetime - 86400s.

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Encryption - AES256; Authentication - SHA512; PFS group - MODP4096; Lifetime – 86400s;

Testing the configuration

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If you have followed all the above steps, your configuration should be finished. But as with any other configuration, it is always wise to test the setup in order to make sure that it works properly.

Using the ipsec status command we can see that IPsec tunnel is successfully established on RUT router. The command output on a RUT device:

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Also, we should be able to access internet routed via Fortigate, we can check it out by pinging 8.8.8.8 and checking what public IP we get by executing this command via command line on RUT device: curl icanhazip.com and ping 8.8.8.8:

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To check if IPsec tunnel is working properly from Fortinet, we can try pinging our RUT device by using this command in command line interface on Fortinetexec ping 192.168.1.1, if you are not able to ping RUT device, try changing the source interface from which we try pinging, by executing this command exec ping-options source 192.168.5.99:

See also

IPsec on Teltonika Networks devices

External links

OpenWrt Ipsec basics

Fortinet Ipsec configuration