Question

Difficulty: MediumIPv6 Static Routing

An engineer needs to configure two IPv6 static routes on a Cisco IOS router:
1. A static route to reach the remote network 2001:db8:3c0d:1::/642001:\text{db8}:3\text{c0d}:1::/64 using the link-local address fe80::1\text{fe80}::1 of the adjacent router connected via interface GigabitEthernet0/0/1\text{GigabitEthernet0/0/1}.
2. A backup (floating) default static route via the global unicast next-hop address 2001:db8:acad:f::12001:\text{db8}:\text{acad}:\text{f}::1 with an Administrative Distance of 130130.

Which TWO IPv6 static route commands correctly fulfill these requirements?

  1. ipv6 route 2001:db8:3c0d:1::/64 GigabitEthernet0/0/1 fe80::1Answer
  2. ipv6 route ::/0 2001:db8:acad:f::1 130Answer
  3. C
    ipv6 route 2001:db8:3c0d:1::/64 fe80::1
  4. D
    ipv6 route ::/0 2001:db8:acad:f::1 1

Answer

The two correct command statements are 'ipv6 route 2001:db8:3c0d:1::/64 GigabitEthernet0/0/1 fe80::1' and 'ipv6 route ::/0 2001:db8:acad:f::1 130'.
The correct command for the specific subnet prefix using a link-local address explicitly provides both the exit interface and the link-local address. The correct backup default route uses '::/0' with an administrative distance of 130, ensuring it functions as a floating static route.

Step-by-Step Solution

1
Analyze link-local next-hop syntax requirements
Link-local addresses (fe80::/10) are non-routable outside the local link. Therefore, Cisco IOS requires the exit interface parameter when using a link-local next-hop (e.g., 'GigabitEthernet0/0/1 fe80::1').
Without the exit interface, the router cannot determine which outgoing interface leads to that link-local neighbor.
2
Identify default route prefix and floating static AD requirements
The IPv6 default route prefix is '::/0'. To make it floating/backup, its administrative distance must be set higher than the primary routing source (in this case, 130).
An AD of 130 ensures the route remains inactive in the routing table until primary routes with lower AD values fail.

Key Concept

IPv6 Static Route Syntax & Link-Local Next-Hop Requirements
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