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Difficulty: MediumIPv6 Static Routing

A network administrator is configuring static routing on router R1 to forward traffic to the destination network 2001:DB8:CAFE:5::/642001:\text{DB8}:\text{CAFE}:5::/64. The egress interface on R1 is GigabitEthernet0/0/0, which connects directly to router R2. Router R2's connected interface has a global unicast address of 2001:DB8:LAB:1::2/642001:\text{DB8}:\text{LAB}:1::2/64 and a link-local address of FE80::2\text{FE80}::2. Which command correctly configures a static route on R1 using R2's link-local address as the next hop?

  1. ipv6 route 2001:DB8:CAFE:5::/64 GigabitEthernet0/0/0 FE80::2Answer
  2. B
    ipv6 route 2001:DB8:CAFE:5::/64 FE80::2
  3. C
    ipv6 route 2001:DB8:CAFE:5::/64 GigabitEthernet0/0/0 FE80::1
  4. D
    ipv6 route 2001:DB8:CAFE:5::/64 2001:DB8:LAB:1::1

Answer

The command 'ipv6 route 2001:DB8:CAFE:5::/64 GigabitEthernet0/0/0 FE80::2' correctly specifies both the local exit interface and the neighbor's link-local next-hop address.
In Cisco IOS, IPv6 static routes using a link-local address as the next-hop MUST be fully specified by including both the local exit interface and the neighbor's link-local IPv6 address. The command specifying both GigabitEthernet0/0/0 and FE80::2 meets this requirement.

Step-by-Step Solution

1
Identify the destination prefix and prefix length.
The target destination network is 2001:DB8:CAFE:5::/642001:\text{DB8}:\text{CAFE}:5::/64.
The first argument of an IPv6 static route in Cisco IOS is always the destination IPv6 prefix/prefix-length.
2
Determine the next-hop requirements when using a link-local address.
Link-local addresses (FE80::/10) are bound strictly to a specific link (interface).
Because the same link-local address can exist on multiple interfaces of the same router, the router cannot determine which egress interface to use unless the exit interface is explicitly stated in the command.
3
Construct the complete fully specified IPv6 static route command.
'ipv6 route 2001:DB8:CAFE:5::/64 GigabitEthernet0/0/0 FE80::2'
This includes the destination prefix, the local interface (GigabitEthernet0/0/0), and the neighbor's link-local address (FE80::2).

Key Concept

IPv6 Static Route Link-Local Next-Hop Syntax Requirement
Estimated Time:1m 30s
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Topics

IPv6 Static Routing

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