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Floating Static Routes: What They Are and Why They Matter

Floating static routes are backup paths that stay hidden in the routing table until a primary route fails. This post explains how administrative distance controls route preference and walks through a practical Cisco IOS configuration example showing automatic failover in action.

Jay Whale

• 3 min read
Floating Static Routes: What They Are and Why They Matter

When you're learning static routing, one of the most practical concepts you'll encounter is the floating static route. It sounds fancy, but the idea is simple: it's a backup path that stays hidden until your primary path fails. Understanding how this works will help you design more resilient networks, and it's a key concept for the CCNA exam.

What Is a Floating Static Route?

A floating static route is a static route configured with a higher administrative distance than the primary route. That higher value causes the router to "prefer" the primary route and only use the floating static route when the primary disappears from the routing table.

To understand why this matters, you need to know what administrative distance (AD) is. AD is a value from 0 to 255 that tells the router how trustworthy a routing source is. Lower AD values are preferred. For reference, here are some common defaults:

  • Connected interface: 0
  • Static route: 1
  • OSPF: 110
  • RIP: 120

When you configure a floating static route, you manually assign it an AD value higher than the primary route. That tells the router: "Only use this route if the preferred one is gone."

A Practical Example

Imagine a small branch office router connected to headquarters via two paths: a primary OSPF-learned route over a dedicated WAN link, and a backup static route over a cheaper broadband connection. You want the OSPF route to win every time it's available, and only fall back to the static route if that link goes down.

Here's how that configuration looks on a Cisco router:

! Primary route learned via OSPF (AD 110) - no action needed, already preferred
! Floating static route for backup - AD set to 200 (higher than OSPF)
ip route 192.168.10.0 255.255.255.0 10.0.2.1 200

That 200 at the end of the command is the administrative distance you're manually assigning. As long as OSPF is advertising a route to 192.168.10.0, the floating static route stays invisible in the routing table. It's there in the configuration, but the router won't use it.

You can verify what's in the routing table with:

Router# show ip route

Codes: C - connected, S - static, O - OSPF
...
O     192.168.10.0/24 [110/20] via 10.0.1.1, 00:05:32, GigabitEthernet0/0

Notice the floating static route doesn't appear here. Now simulate the OSPF link failing by shutting down the interface. The OSPF route disappears, and the router installs the floating static route automatically:

Router# show ip route

S     192.168.10.0/24 [200/0] via 10.0.2.1

The S confirms it's a static route, and the [200/0] shows the AD of 200 and a metric of 0. Network connectivity is restored without any manual intervention.

Why Floating Static Routes Matter for Network Resilience

Floating static routes give you automatic failover without running a full dynamic routing protocol on every link. This is especially useful in scenarios like:

  • Backup WAN links: Use a secondary broadband or LTE connection only when the primary fails
  • Mixed environments: Combine dynamic routing (OSPF, EIGRP) with static backup paths where dynamic routing isn't feasible
  • Simple branch sites: Provide redundancy without the complexity of running a dynamic protocol on every connection

The key advantage is that this failover is automatic. When the primary route returns, the router drops the floating static route from the routing table and goes back to the preferred path, again without any manual intervention.

One Thing to Watch Out For

Floating static routes depend on the primary route disappearing from the routing table. If the routing protocol loses its neighbor but the interface stays up (a common scenario with WAN links), the router may never remove the primary route, so the floating static never kicks in. This is worth keeping in mind as you design your backup path strategy.

What's Next

Now that you understand floating static routes, the next step is getting hands-on with both IPv4 and IPv6 static routing configurations. In the next post, we'll walk through configuring and verifying static routes on a Cisco router, covering both address families with full CLI examples.

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If you want to see floating static route failover in action on a live network, a tool like PRTG Network Monitor can alert you the moment a backup path becomes active, giving you visibility into exactly when and why your primary route disappeared. PRTG Network Monitor, SolarWinds Network Performance Monitor and Nagios.

Tools and resources for this topic