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Difficulty: MediumIPv4 Static Routing

A network administrator is configuring IPv4 static routes on router R1. The administrator must implement a primary default static route pointing to next-hop IP address 203.0.113.1203.0.113.1, as well as a backup floating static route for destination subnet 172.16.10.0/24172.16.10.0/24 via next-hop IP 192.168.1.2192.168.1.2. The backup route must take effect only if the primary path learned via OSPF (Administrative Distance of 110) becomes unavailable. Which two commands must the administrator execute on router R1 to satisfy these requirements? (Select two.)

  1. ip route 0.0.0.0 0.0.0.0 203.0.113.1Answer
  2. ip route 172.16.10.0 255.255.255.0 192.168.1.2 120Answer
  3. C
    ip route 0.0.0.0 255.255.255.255 203.0.113.1
  4. D
    ip route 172.16.10.0 255.255.255.0 192.168.1.2 90

Answer

The administrator must configure the default route using `ip route 0.0.0.0 0.0.0.0 203.0.113.1` and the floating static backup route using `ip route 172.16.10.0 255.255.255.0 192.168.1.2 120`.
The default route requires the prefix and mask `0.0.0.0 0.0.0.0` pointing to next-hop 203.0.113.1203.0.113.1. To serve as a backup to an OSPF route with an Administrative Distance of 110, the floating static route must specify an Administrative Distance higher than 110, which the command specifying an AD of 120 accomplishes.

Step-by-Step Solution

1
Determine the standard command syntax for an IPv4 default static route.
A default route matches all destination networks using prefix 0.0.0.00.0.0.0 and mask 0.0.0.00.0.0.0, forming the command `ip route 0.0.0.0 0.0.0.0 203.0.113.1`.
Quad-zero notation (0.0.0.0 0.0.0.0) is required in Cisco IOS to represent any unlisted IPv4 destination.
2
Calculate the necessary Administrative Distance for a floating static route intended to back up OSPF.
OSPF has a default Administrative Distance of 110. The backup static route requires an Administrative Distance higher than 110 (such as 120).
Cisco routers select routes based on the lowest Administrative Distance. A higher AD keeps the static route inactive until the primary OSPF route is removed from the routing table.

Key Concept

IPv4 Default Static Route Syntax and Floating Static Route Administrative Distance Selection
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Topics

IPv4 Static Routing

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