Multi-WAN with opnSense

opnSense make it pretty easy to support and manage multiple Internet Service Providers (ISP), also called multi-wan.

The basic idea is that you have two (or more…) upstream connections to the internet, via different providers. Each one is connected to your opnSense using a specific dedicated interface, ethernet or USB/Ethernet.

I will assume the following:

• ISP1 is connected to ethernet port 1, interface called WAN
• ISP2 is connected to ethernet port 2, interface called ISP2

opnSense lets you configure your interfaces both for failover and load balancing. I will show you how to set them up for failover.

You will use your primary ISP (faster, better?) as usual, but when it goes down, the secondary ISP (slower maybe?) will kick-in and replace it until it comes back up. This is all automatically managed by opnSense, all you need to do is:

• Configure the gateway for each ISP
• Assign a test IP for each gateway
• Define a gateway group, assign both gateways with different priority

The complete process is described pretty well here and i will not get into details.

A few notes, which might save you time:

• Remember to assign different test IPs, and use test IPs which are solid like google or cloudflare's DNS services
• Remember to enable the IP checking, of the gateway will not be tested for connectivity by default

Also, something which proved useful to me, was to configure Unbound DNS forwarder using public DNS records which are not linked to a specific ISP, like the google or cloudflare or even AdGuard DNS servers.