A network administrator is configuring a backup floating static route on router R1 to reac… — Cisco CCNA

A network administrator is configuring a backup floating static route on router R1 to reach the internal subnet $10.20.0.0/16$ . The primary path to this destination is currently learned dynamically via OSPF, which has a default Administrative Distance of $110$ . The backup route should traverse next-hop IPv4 address $192.168.12.2$ and must enter the routing table only when the primary OSPF path becomes unavailable. Which Cisco IOS command correctly achieves this objective?

ip route 10.20.0.0 255.255.0.0 192.168.12.2 120Answer
B
ip route 10.20.0.0 255.255.0.0 192.168.12.2 90
C
ip route 10.20.0.0 255.255.0.0 192.168.12.2 110
D
ip route 10.20.0.0 0.0.255.255 192.168.12.2 120

Answer

The correct command is 'ip route 10.20.0.0 255.255.0.0 192.168.12.2 120'.

A floating static route is configured by specifying an administrative distance higher than that of the primary routing protocol. Since OSPF has an Administrative Distance of 110, setting an AD of 120 ensures the static route remains untracked in the routing table during normal operation and only activates if the primary OSPF route drops out.

Step-by-Step Solution

Determine the destination prefix and subnet mask for 10.20.0.0/16.

Destination prefix is 10.20.0.0 and the 16-bit subnet mask in dotted-decimal format is 255.255.0.0.

Cisco IOS static route syntax uses subnet masks rather than wildcard masks.

Identify the next-hop IP address.

Next-hop IP address is 192.168.12.2.

The scenario explicitly designates 192.168.12.2 as the exit path for backup traffic.

Select an Administrative Distance (AD) greater than the primary route's AD.

OSPF default AD is 110; therefore, the floating static route requires an AD greater than 110 (such as 120).

Routers prefer lower Administrative Distance values. Assigning a value higher than 110 ensures the static route remains inactive in the routing table until OSPF fails.

Key Concept

Floating Static Routes and Administrative Distance

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