Understanding first hop redundancy

Let's imagine that, within your organization, each device is configured to use a specific IP address as its default gateway to the internet. What if that IP address or device goes offline? How will your client devices reach the internet?

The following diagram shows the default gateway going down, thus preventing clients from reaching the internet:

Figure 8.54 – Default gateway goes offline

You may be thinking, we can replace the router with another and apply the same configurations to it and our internet connectivity will be restored. This is a workable solution, but it's not too efficient because it's a reactive solution and requires too many interventions.

What if we could implement redundancy on the default gateway to ensure that, if the main router goes down, there's another device that will act as the new default gateway, without us having to change the default gateway's IP address...