Setting up a Site to Site VPN on OPNsense using Tailscale

Preporation

In preporation for following the steps in this guide it is assumed that tailscale is installed on OPNsense using the plugin (setup guide) and that your remote site has a subnet router setup advertising a route to tailscale

Setup

Tailscale

1. Navigate to VPN > Tailscale > Settings
2. Select Advanced
3. Enable Accept Routes and Disable SNAT
4. Select Apply

Gateways and routes

1. Navigate to System > Gateway > Configuration
2. Select +
3. Configure the gateway as shown below
4. Select Save
5. Select Apply
6. Navigate to System > Routes > Configuration
7. Select +
8. Fill in your remote network and select the tailscale gateway
9. Select Save
10. Select Apply

Fix Mobile Remote Access

due to disabling Source NAT within Tailscale we need to configure a route so that our LAN hosts know how to reach any remote workstations or phones via Tailscale

1. Navigate to Services > ISC DHCPv4 > LAN
2. Locate Additional Options and Select Advanced
3. Enter 121 under Number
4. Select String for Type
5. Enter the string Generated at Medo64.com for Value