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Difficulty: HardIPv6 Static Routing

A network administrator is configuring a floating static route on router R1 to reach the destination prefix 2001:db8:acad:10::/642001:\text{db8}:\text{acad}:10::/64. The primary path to this network is currently learned via OSPFv3 with an Administrative Distance of 110. The administrator wants to configure the backup static route using the next-hop neighbor's link-local IPv6 address fe80::2fe80::2 across R1's local interface GigabitEthernet0/1. Which command must be entered on R1 to correctly configure this floating static route?

  1. ipv6 route 2001:db8:acad:10::/64 GigabitEthernet0/1 fe80::2 120Answer
  2. B
    ipv6 route 2001:db8:acad:10::/64 fe80::2 120
  3. C
    ipv6 route 2001:db8:acad:10::/64 GigabitEthernet0/1 fe80::2 90
  4. D
    ipv6 route 2001:db8:acad:10::/64 fe80::fffe:2 GigabitEthernet0/1 120

Answer

The command 'ipv6 route 2001:db8:acad:10::/64 GigabitEthernet0/1 fe80::2 120' is the correct configuration.
The option specifying 'ipv6 route 2001:db8:acad:10::/64 GigabitEthernet0/1 fe80::2 120' uses the valid Cisco IOS syntax for a fully specified static route using a link-local next hop. The local exit interface GigabitEthernet0/1 resolves link-local address ambiguity, and an Administrative Distance of 120 ensures the route functions correctly as a floating static backup to the active OSPFv3 route (AD 110).

Step-by-Step Solution

1
Identify the mandatory components of an IPv6 static route using a link-local address.
Because IPv6 link-local addresses (fe80::/10) are non-routable outside their local link, Cisco IOS requires both the local exit interface and the link-local next-hop address (fully specified static route).
Without specifying the exit interface, the router cannot determine which local segment contains the target fe80::2 address.
2
Determine the required Administrative Distance for a floating static route.
The primary route is OSPFv3 with AD = 110. The floating static route AD must be greater than 110 (e.g., 120).
Setting an AD higher than the primary routing protocol ensures the static route remains inactive in the routing table until the primary OSPFv3 route fails.
3
Verify Cisco IOS syntax order.
The syntax structure is 'ipv6 route <prefix/length> <exit-interface> <link-local-address> [administrative-distance]'.
The correct command syntax specifies interface GigabitEthernet0/1 followed by next-hop fe80::2 and AD 120.

Key Concept

Fully Specified IPv6 Static Route and Floating Static Route AD Configuration
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Topics

IPv6 Static Routing

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