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Difficulty: HardIPv6 Static Routing

A network operations engineer is provisioning IPv6 static routing on router Edge-Rtr. The design requirements specify:
1. All default traffic must be forwarded to the primary service provider gateway at global unicast address 2001:db8:1000:1::12001:\text{db8}:1000:1::1.
2. A backup static route for internal network 2001:db8:abc:10::/642001:\text{db8}:\text{abc}:10::/64 must direct traffic to link-local next-hop address fe80::2\text{fe80}::2 across exit interface GigabitEthernet0/0/1, functioning as a floating route to back up a primary OSPFv3 route (administrative distance 110).

Which TWO Cisco IOS configuration commands correctly fulfill these requirements?

  1. ipv6 route ::/0 2001:db8:1000:1::1Answer
  2. ipv6 route 2001:db8:abc:10::/64 GigabitEthernet0/0/1 fe80::2 120Answer
  3. C
    ipv6 route 2001:db8:abc:10::/64 fe80::2 120
  4. D
    ipv6 route 2001:db8:abc:10::/64 GigabitEthernet0/0/1 fe80::2 90

Answer

The correct commands are 'ipv6 route ::/0 2001:db8:1000:1::1' for default routing to the global unicast address, and 'ipv6 route 2001:db8:abc:10::/64 GigabitEthernet0/0/1 fe80::2 120' for the fully-specified floating static route.
The command configuring the default prefix '::/0' to the global unicast address correctly establishes default forwarding. The command referencing prefix '2001:db8:abc:10::/64' with interface 'GigabitEthernet0/0/1', link-local address 'fe80::2', and administrative distance '120' correctly satisfies all syntax rules for link-local next hops and floating route precedence.

Step-by-Step Solution

1
Identify the proper prefix and syntax for an IPv6 default static route.
The IPv6 default route prefix is ::/0::/0. When using a global unicast next hop, specifying an exit interface is optional.
Global unicast addresses are globally reachable and routable without explicit interface disambiguation.
2
Identify the mandatory syntax requirements when using an IPv6 link-local address as a next-hop.
Because link-local addresses (FE80::/10) are non-routable outside their local link, Cisco IOS requires specifying the local outbound exit interface along with the link-local next-hop address.
Without specifying the exit interface, the router cannot determine which local interface connects to the target link-local neighbor.
3
Evaluate the administrative distance requirement for floating static routes.
The floating static route must have an administrative distance greater than the active route protocol (OSPFv3 AD = 110), so an AD of 120 is required.
Routes with lower administrative distance values take priority in the routing table.

Key Concept

IPv6 static route configuration syntax, link-local next-hop requirements, and floating static route administrative distance manipulation.
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Topics

IPv6 Static Routing

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