A network engineer is configuring a dual-homed router connecting a remote office to the corporate headquarters. The primary WAN connection dynamically receives routes via OSPF, while a secondary LTE backup link is configured using a static route to the same destination network (). The administrator wants the router to automatically prefer the OSPF route under normal operations and fall back to the static route only if the primary OSPF link fails. Given that default administrative distance (AD) values are used for OSPF, which administrative distance should the administrator manually assign to the backup static route?
- A1
- B90
- C110
- 120Answer
Answer
The administrator should assign an administrative distance higher than OSPF's default value of 110 (such as 120) to create a floating static route that only becomes active when the primary link fails.
To configure a floating static route that serves strictly as a backup path, the static route must be configured with an Administrative Distance (AD) higher than that of the primary dynamic routing protocol. Because OSPF has a default AD of 110, setting the static route's AD to a value such as 120 ensures that the router installs the OSPF route into the routing table during normal operation. The static route will only be installed into the routing table if the primary OSPF route becomes unavailable.
Step-by-Step Solution
Key Concept
Floating Static Routes and Administrative Distance Hierarchy
Estimated Time:1m 30s