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Difficulty: HardIPv4 Static Routing

A branch router receives an external EIGRP route (EIGRP EX, Administrative Distance of 170) for the corporate subnet 10.200.0.0/1610.200.0.0/16 over a primary MPLS link. A network administrator must configure a floating static backup route for 10.200.0.0/1610.200.0.0/16 using the secondary ISP next-hop address 192.168.1.2192.168.1.2. The backup path must only be installed in the IPv4 routing table if the primary EIGRP EX path becomes unavailable. Which command must be configured on the router to achieve this requirement?

  1. ip route 10.200.0.0 255.255.0.0 192.168.1.2 175Answer
  2. B
    ip route 10.200.0.0 255.255.0.0 192.168.1.2 90
  3. C
    ip route 10.200.0.0 255.255.0.0 192.168.1.2 170
  4. D
    ip route 10.200.0.0 0.0.255.255 192.168.1.2 175

Answer

The command 'ip route 10.200.0.0 255.255.0.0 192.168.1.2 175' correctly configures the floating static route.
A floating static route acts as a backup path and must have an Administrative Distance (AD) strictly higher than the primary route currently in use. Because External EIGRP routes have a default AD of 170, the backup static route must be configured with an AD greater than 170 (such as 175). Furthermore, Cisco IOS static route syntax requires the destination network mask to be specified as a standard subnet mask (255.255.0.0) rather than a wildcard mask.

Step-by-Step Solution

1
Identify the primary route's Administrative Distance (AD).
External EIGRP (EIGRP EX) routes have a default Administrative Distance of 170.
Floating static routes must have an AD higher than the primary route's AD to remain inactive in the routing table until failure occurs.
2
Determine the required Administrative Distance for the floating static route.
The static route AD must be strictly greater than 170 (e.g., 175).
Cisco IOS selects routes with lower AD values first. A higher AD keeps the route out of the routing table while the primary path is active.
3
Verify Cisco IOS IPv4 static route syntax requirements.
The proper command structure is 'ip route <destination-prefix> <subnet-mask> <next-hop-ip> [distance]'.
Static IPv4 routing in Cisco IOS requires a standard dotted-decimal subnet mask (255.255.0.0 for /16), not an OSPF/ACL wildcard mask.

Key Concept

Floating static route configuration requiring higher Administrative Distance than dynamic primary routes
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Topics

IPv4 Static Routing

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