Cisco CCNA (200-301)IP ConnectivityHard
A network engineer needs to configure a static IPv6 route to the network 2001:db8:200::/64. The next-hop router's link-local address is FE80::1 on the local router's GigabitEthernet0/0 interface. Which command correctly configures this route?
- A`ipv6 route 2001:db8:200::/64 GigabitEthernet0/0 FE80::1`
- B`ipv6 route 2001:db8:200::/64 GigabitEthernet0/0`
- C`ipv6 route 2001:db8:200::/64 FE80::1`
- D`ipv6 route 2001:db8:200::/64 FE80::1 GigabitEthernet0/0`
Show answer & explanationAnswer & explanation
Correct answer: A. `ipv6 route 2001:db8:200::/64 GigabitEthernet0/0 FE80::1`
When configuring an IPv6 static route with a link-local next-hop address, it is mandatory to also specify the exit interface. This is because link-local addresses are only unique on a single link, so the router needs to know which interface to use to reach that specific link-local address. Without the exit interface, the router cannot determine the correct link.
Why the other options are wrong
- B. While specifying an exit interface is possible for IPv6 static routes, for a link-local next-hop, the next-hop address *must* also be included.
- C. This command is incomplete for a link-local next-hop. The exit interface is missing.
- D. The order of exit interface and next-hop IP is important. The correct syntax is `ipv6 route [destination-prefix/length] [interface-type interface-number] [ipv6-address]`.
IPv6 Static Route with Link-Local Next-Hop
When configuring an IPv6 static route using a link-local address as the next-hop, both the next-hop link-local address AND the local exit interface must be specified.
- Link-local addresses are unique only on a single link.
- Router needs the exit interface to know which link to send traffic out.
- Syntax: `ipv6 route [prefix/len] [interface] [link-local-address]`.
- Prevents ambiguity in next-hop resolution.
Memory trick: Link-local needs its Link, to know where to think.