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Zorluk: ZorFloating Static Routes

A network engineer inspects a router configuration designed to provide a redundant secondary path to a branch subnet 10.240.12.0/2410.240.12.0/24. The primary path to this destination is dynamically learned via OSPF (default Administrative Distance of 110110). The engineer finds the following static route entry in the running configuration:

`ip route 10.240.12.0 255.255.255.0 192.168.1.2 95`

During normal operation with the OSPF link operational, traffic continues to traverse the backup link. Which TWO statements accurately explain this behavior and the required configuration fix?

  1. The configured static route takes precedence over the OSPF route because its configured administrative distance of 9595 is lower than the OSPF default administrative distance of 110110.Cevap
  2. Reconfiguring the static route with an administrative distance greater than 110110 allows OSPF to act as the primary route while maintaining the static route as a floating backup.Cevap
  3. C
    The router load-balances traffic between OSPF and the static route because static routes automatically inherit the metric of active dynamic protocols.
  4. D
    Changing the static route's administrative distance to 9090 will deactivate the static route and restore the OSPF path into the routing table.

Cevap

The static route currently pre-empts OSPF because its administrative distance (9595) is lower than OSPF's default (110110). To function correctly as a floating backup, the static route's administrative distance must be set to a value greater than 110110.
Cisco IOS routing table selection relies strictly on Administrative Distance (AD) when comparing routes learned from different sources for the exact same network prefix. OSPF has a default AD of 110110. The configured static route has an AD explicitly set to 9595. Because 9595 is lower than 110110, the router prefers the static route, placing it into the routing table and routing all traffic across the backup link. To convert this into a functional floating static route, the AD of the static route must be increased to a value higher than 110110 (for example, 120120), allowing OSPF to be preferred while the primary link is healthy.

Adım Adım Çözüm

1
Analyze the Administrative Distance (AD) of the primary path protocol.
OSPF has a standard Cisco IOS default AD of 110110.
Routing decisions prioritize paths with the lowest administrative distance when identical prefix lengths are compared.
2
Evaluate the configured static route's AD.
The command `ip route 10.240.12.0 255.255.255.0 192.168.1.2 95` assigns an explicit AD of 9595.
Since 95<11095 < 110, the router installs the static route into the routing table as the active route, suppressing the OSPF route.
3
Determine the required administrative distance for a floating static route.
The static route's AD must be set higher than the primary path (>110> 110), such as 120120 or 130130.
A floating static route remains out of the routing table until the primary lower-AD route is removed due to network topology changes or link failure.

Anahtar Kavram

Floating static routes rely on configuring an Administrative Distance higher than the primary dynamic routing protocol.
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Floating Static Routes

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