A floating static route is a static route that has been configured with a higher administrative distance than the primary route to the same destination. This creates a backup routing path that remains inactive in the routing table until the primary route fails or becomes unavailable.
In Cisco netw…A floating static route is a static route that has been configured with a higher administrative distance than the primary route to the same destination. This creates a backup routing path that remains inactive in the routing table until the primary route fails or becomes unavailable.
In Cisco networking, every routing protocol and route type has an administrative distance (AD) value that determines its trustworthiness. Lower AD values are preferred over higher ones. For example, a directly connected route has an AD of 0, a static route has an AD of 1, EIGRP has an AD of 90, and OSPF has an AD of 110.
When you configure a floating static route, you manually assign it a higher administrative distance than the primary route. For instance, if your primary route is learned through OSPF with an AD of 110, you would configure your floating static route with an AD of 120 or higher. This ensures the static route only appears in the routing table when the OSPF route is no longer available.
The configuration syntax on a Cisco router is: ip route [destination network] [subnet mask] [next-hop address or exit interface] [administrative distance]
For example: ip route 192.168.10.0 255.255.255.0 10.1.1.1 150
This command creates a static route to 192.168.10.0/24 via next-hop 10.1.1.1 with an AD of 150. If a dynamic routing protocol is advertising the same destination with a lower AD, that route will be preferred.
Floating static routes are commonly used for backup WAN links, providing redundancy when the primary connection fails. They offer a simple and effective failover mechanism that requires minimal configuration. When the primary path recovers, the floating static route automatically becomes inactive again as the preferred route with the lower administrative distance is reinstated in the routing table.
Floating Static Route - Complete Guide for CCNA
What is a Floating Static Route?
A floating static route is a static route configured with a higher administrative distance (AD) than the primary route to the same destination. This creates a backup route that remains inactive in the routing table until the primary route fails.
Why is it Important?
Floating static routes provide network redundancy and fault tolerance. They act as backup paths that automatically activate when the primary route becomes unavailable, ensuring continuous network connectivity. This is especially valuable in scenarios where:
- You have a primary dynamic routing protocol (like OSPF or EIGRP) and want a static backup - You need a failover mechanism between two ISP connections - Business-critical applications require high availability
How it Works
Administrative distance determines route preference - lower AD values are preferred. Default AD values include:
When you configure a static route with a higher AD than your primary route, it becomes a floating static route. For example, if OSPF (AD 110) is your primary routing protocol, you would configure a static route with AD 111 or higher.
Configuration Example:
ip route 192.168.10.0 255.255.255.0 10.0.0.2 120
In this command, 120 is the administrative distance, making it less preferred than OSPF routes but still available as backup.
Key Characteristics:
- Does NOT appear in the routing table while the primary route is active - Automatically installs when the primary route is withdrawn - Automatically withdraws when the primary route returns - Requires manual configuration of a higher AD value
Exam Tips: Answering Questions on Floating Static Route
1. Remember the AD requirement: A floating static route MUST have a higher AD than the primary route to function correctly.
2. Know default AD values: Memorize administrative distances for common routing protocols. Questions often test whether you understand which AD value to assign.
3. Understand visibility: If asked why a static route does not appear in the routing table, consider that it might be a floating static route with a better path available.
4. Recognize the syntax: The AD value is placed at the end of the ip route command. Look for that extra number after the next-hop address or exit interface.
5. Scenario-based questions: When a question describes backup paths or failover scenarios, floating static routes are likely the answer.
6. Watch for tricky wording: Questions may describe the behavior rather than use the term floating static route. Phrases like backup static route or standby route often refer to floating static routes.
7. Verification commands: Know that show ip route will only display the floating static route when it is active. Use show ip route static to see configured static routes.
8. Common exam scenario: Primary link uses EIGRP (AD 90), backup uses floating static with AD 91 or higher. If asked what AD to use, choose any value greater than the primary routing protocol AD.