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Difficulty: MediumFloating Static Routes

Router R1 learns the destination prefix 172.16.10.0/24172.16.10.0/24 dynamically via OSPF with a default Administrative Distance of 110. A network administrator needs to implement a floating static route to 172.16.10.0/24172.16.10.0/24 via next-hop IP 192.168.12.2192.168.12.2 to serve as a backup path.

Which TWO statements correctly describe the configuration requirements and routing table behavior for this floating static route? (Select TWO.)

  1. The floating static route must be configured with an Administrative Distance greater than 110 (such as 120).Answer
  2. The floating static route remains in R1's running configuration but is excluded from the active routing table while the primary OSPF route is active.Answer
  3. C
    Configuring an Administrative Distance of 90 for the static route ensures it functions as an inactive backup route until OSPF fails.
  4. D
    If the static route is assigned an Administrative Distance equal to 110, the router will perform equal-cost load balancing between OSPF and the static route.

Answer

The floating static route must be configured with an Administrative Distance higher than the primary routing protocol (greater than 110 for OSPF), and it will remain stored in the router configuration without appearing in the routing table until the primary route fails.
A floating static route acts as a backup path and is created by manually configuring a static route with an Administrative Distance higher than that of the primary routing protocol. Since the primary route is OSPF with an AD of 110, setting the static route AD higher (e.g., 120) prevents it from being installed in the active routing table under normal operating conditions. It remains stored in the router configuration and is installed into the routing table only if the primary OSPF route disappears.

Step-by-Step Solution

1
Identify the Administrative Distance (AD) of the primary path protocol.
OSPF has a default Administrative Distance of 110.
Administrative Distance indicates the trustworthiness of the route source. Lower AD values are preferred.
2
Determine the AD required for a floating static backup route.
The AD must be set to a value strictly greater than 110 (e.g., 120 or 130).
Setting the AD higher ensures the static route is less preferred than OSPF during normal network operations.
3
Analyze how Cisco IOS processes inactive floating static routes.
The backup static route is maintained in the running configuration but omitted from the active IP routing table.
The routing table only installs the route with the lowest AD for any given destination network prefix.

Key Concept

Floating Static Route Administrative Distance Requirements
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Topics

Floating Static Routes

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