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Difficulty: EasyFloating Static Routes

A network administrator is configuring a static backup route to take over if an existing primary route learned via OSPF (Administrative Distance 110) fails. Which TWO statements describe requirements for this floating static route to function correctly as a backup?

  1. The static route must be configured with an administrative distance value greater than 110.Answer
  2. The primary OSPF route must be removed from the routing table before the floating static route can be installed.Answer
  3. C
    The static route must be configured with an administrative distance value lower than 110.
  4. D
    The static route must be configured with an administrative distance value equal to 110.

Answer

The static route must be configured with an administrative distance value greater than 110, and the primary OSPF route must be removed from the routing table before the floating static route can be installed.
A floating static route serves as a backup path by configuring an administrative distance higher than that of the primary route (greater than 110 for an OSPF primary route). Because routers prefer paths with lower administrative distance, the floating static route will only be installed into the routing table after the primary route fails and is removed.

Step-by-Step Solution

1
Evaluate the Administrative Distance requirement for backup routes.
Because OSPF has a default Administrative Distance (AD) of 110, a floating static route intended as a backup must be configured with an AD higher than 110 (such as 120).
Cisco IOS selects the route with the lowest AD value to place into the routing table.
2
Determine the condition under which the floating static route becomes active.
The floating static route remains inactive and out of the routing table until the primary OSPF route is lost or removed.
As long as the primary route with a lower AD exists in the routing table, higher-AD routes are kept in reserve.

Key Concept

Floating static routes use a higher Administrative Distance than the primary route protocol so they only enter the routing table when the primary route fails.
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Topics

Floating Static Routes

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