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Zorluk: OrtaFloating Static Routes

An administrator intends to deploy a floating static route on router R1 to serve as a backup path for internal network 10.100.50.0/2410.100.50.0/24, which is primarily learned via Internal EIGRP (administrative distance 90). Following the configuration, traffic immediately shifts to the secondary link despite the primary link remaining fully operational.

Which configuration mistake caused the static route to preempt the primary EIGRP route in the routing table?

  1. The static route was assigned an administrative distance value lower than 90, causing it to take precedence over the EIGRP route.Cevap
  2. B
    The static route was configured with an administrative distance of 110, which automatically overrides Internal EIGRP routes.
  3. C
    The static route omitted the next-hop IP address and specified an egress interface, forcing an administrative distance of 0.
  4. D
    The static route lacked an IP SLA track object, which is mandatory for floating static routes to remain inactive.

Cevap

The static route was assigned an administrative distance value lower than 90, causing it to take precedence over the EIGRP route.
Cisco IOS routers evaluate Administrative Distance (AD) to determine which routing source to trust when multiple sources offer routes to the exact same destination prefix. Lower AD values are preferred. Internal EIGRP has a default AD of 90. For a static route to serve as a floating backup, its AD must be configured to a value strictly greater than 90 (e.g., 95 or 130). If the administrator configures an AD lower than 90 (or omits the AD parameter, which defaults to 1), the static route will be preferred over EIGRP and immediately installed into the routing table as the active route.

Adım Adım Çözüm

1
Analyze the primary routing protocol's Administrative Distance (AD).
Internal EIGRP has a default AD of 90.
Cisco IOS selects routes with the lowest administrative distance when multiple sources advertise the identical destination network prefix.
2
Determine the requirement for a floating static route to act as a backup.
The floating static route must have an AD strictly greater than 90 so it stays out of the routing table while EIGRP is active.
If the configured static route has an AD lower than 90 (or defaults to 1), the router prefers the static route over EIGRP immediately.
3
Identify the cause of immediate preemption.
Assigning an AD lower than 90 caused the router to install the static route into the routing table over the active EIGRP route.
Routes with lower administrative distance values take administrative preference in the Cisco IOS routing table installation process.

Anahtar Kavram

Administrative Distance Precedence in Floating Static Routes
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