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Difficulty: EasyIPv4 Static Routing

A network engineer wants to configure a floating static route to serve as a backup to a primary route learned via OSPF, which has an Administrative Distance of 110. Which Administrative Distance value should be specified in the static route command so that it is only installed in the routing table when the OSPF route fails?

  1. 120Answer
  2. B
    110
  3. C
    90
  4. D
    1

Answer

The correct administrative distance is 120 because a floating static route must have an administrative distance higher than the primary routing protocol (OSPF AD 110) to remain inactive until the primary route fails.
A floating static route acts as a backup route and is configured with an Administrative Distance higher than that of the primary routing protocol. Since OSPF has an AD of 110, setting the static route's AD to 120 keeps it out of the routing table until the primary OSPF route becomes unavailable.

Step-by-Step Solution

1
Identify the Administrative Distance (AD) of the primary routing protocol.
The primary route is learned via OSPF, which has a default AD of 110.
Administrative Distance determines route trustworthiness, where a lower AD value is preferred.
2
Determine the required AD relationship for a floating (backup) static route.
The floating static route must be configured with an AD strictly greater than 110.
If the static route has a lower or equal AD, it will be preferred over or compete with the primary OSPF route.
3
Select the valid option that satisfies the backup requirement.
An AD of 120 is greater than 110 and represents standard backup static routing behavior.
120 is higher than 110, ensuring the route stays in floating status until the OSPF route fails.

Key Concept

Floating Static Route Administrative Distance Configuration
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Topics

IPv4 Static Routing

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