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Difficulty: MediumIPv6 Static Routing

A network administrator is configuring static routing on Cisco router Branch-R1 to reach remote subnet 2001:db8:3c4d:15::/642001:\text{db8}:3\text{c4d}:15::/64. The routing design requires a primary path using next-hop global unicast address 2001:db8:3c4d:12::22001:\text{db8}:3\text{c4d}:12::2, and a floating static backup path using link-local next-hop address fe80::2\text{fe80}::2 reachable via interface GigabitEthernet0/0/1. Which two commands must be configured on Branch-R1 to fulfill these requirements? (Select two.)

  1. ipv6 route 2001:db8:3c4d:15::/64 2001:db8:3c4d:12::2Answer
  2. ipv6 route 2001:db8:3c4d:15::/64 GigabitEthernet0/0/1 fe80::2 130Answer
  3. C
    ipv6 route 2001:db8:3c4d:15::/64 fe80::2 130
  4. D
    ipv6 route 2001:db8:3c4d:15::/64 GigabitEthernet0/0/1 fe80::2 1

Answer

The correct commands are 'ipv6 route 2001:db8:3c4d:15::/64 2001:db8:3c4d:12::2' for the primary route and 'ipv6 route 2001:db8:3c4d:15::/64 GigabitEthernet0/0/1 fe80::2 130' for the floating static backup route.
For the primary path, specifying the destination IPv6 prefix and the global unicast next-hop address provides sufficient forwarding information to the routing table. For the backup path, using a link-local IPv6 address requires a fully specified route format that explicitly includes the exit interface (GigabitEthernet0/0/1), combined with an administrative distance greater than 1 (such as 130) so that it functions as a floating backup route.

Step-by-Step Solution

1
Identify the proper syntax for a primary IPv6 static route using a global unicast next-hop address.
The command syntax is 'ipv6 route <destination-prefix/prefix-length> <global-unicast-next-hop>'. This maps to 'ipv6 route 2001:db8:3c4d:15::/64 2001:db8:3c4d:12::2'.
Global unicast addresses are uniquely identifiable across interfaces, so specifying an exit interface is optional.
2
Identify the mandatory components when configuring a fully specified IPv6 static route with a link-local next-hop address.
Because link-local addresses (fe80::/10) are reused across multiple physical links, Cisco IOS demands both the local exit interface and the link-local address.
Without the local exit interface, the router cannot determine which physical link to transmit packets on to reach fe80::2.
3
Determine the administrative distance requirement for a floating static route.
Assign an administrative distance higher than the primary route's default AD of 1 (e.g., 130).
A higher administrative distance ensures the route remains inactive in the IPv6 routing table until the primary route fails.

Key Concept

IPv6 Static Route Syntax and Link-Local Next-Hop Requirements
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Topics

IPv6 Static Routing

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