IPv6 Practice Questions

Answers and explanations appear when you work through the set above.

1. An engineer configures ipv6 address 2001:db8:0:1::1/64 on an interface but never issues ipv6 unicast-routing globally. What is true about that interface?

   • The interface will refuse to accept the IPv6 address configuration
   • IPv6 and link-local addressing work, but IPv6 forwarding between interfaces stays disabled
   • The address will only work for IPv4-mapped traffic
   • The router will automatically enable unicast routing the first time an address is applied

2. Which command configures an EUI-64 global unicast IPv6 address on an interface, letting the router derive the interface identifier from the MAC address?

   • ipv6 address 2001:db8:0:1::/64 eui-64
   • ipv6 address autoconfig
   • ipv6 address 2001:db8:0:1::1/64 anycast
   • ipv6 address 2001:db8:0:1::1/64

3. Which command manually assigns a specific link-local IPv6 address to an interface instead of letting the router auto-generate one?

   • ipv6 address fe80::1 link-local
   • ipv6 address 2001:db8::1/64
   • ipv6 address fe80::/64 eui-64
   • ipv6 enable

4. An engineer enables IPv6 on a Cisco IOS interface without manually setting a link-local address. The interface then shows FE80::20D:BDFF:FE2D:27D4. What generated it?

   • It was manually typed by the administrator as part of the global address
   • IOS automatically creates a link-local address when IPv6 is enabled
   • It came from a DHCPv6 server on the network
   • It is the router's IPv6 loopback address

5. Which command displays a router's IPv6 interfaces along with their assigned link-local and global unicast addresses in a compact format?

   • show ipv6 route
   • show ipv6 interface brief
   • show ip interface brief
   • show ipv6 neighbors | include REACH

6. What is the correct compressed form of the IPv6 address 2001:0db8:0000:0001:0000:0000:0000:0001?

   • 2001:db8:0:1::1
   • 2001:db8::1:1
   • 2001:db8:1::1
   • 2001:0db8:1::0001

7. In an IPv6 address such as 2001:db8:0:1::/64, what does the /64 prefix length indicate compared to typical IPv4 subnetting?

   • Only 64 total addresses are available in the subnet
   • The first 64 bits are the network prefix; the other 64 are the LAN interface ID
   • The address uses a variable-length subnet mask like IPv4 classful addressing
   • 64 is the maximum number of hosts allowed in the segment

8. Two routers each have IPv6 addresses configured on a shared segment but ipv6 unicast-routing has not been enabled on either. Can they still ping each other's global unicast addresses?

   • Without unicast routing, neither router can send IPv6 traffic or use a global unicast address
   • Yes, same-link pings require no inter-interface forwarding
   • The routers must form an OSPFv3 adjacency before either can reply to ICMPv6
   • Both routers must configure a DHCPv6 relay before they can exchange same-link pings

9. A PC with a static IPv6 address can reach local peers. Its route table has no default route or specific route to a remote test subnet. Which change addresses this routing gap?

   • Configure a default route or learn a router through RAs
   • IPv6 does not support static addressing on end hosts
   • The subnet mask length must always be /48 for hosts to route off-subnet
   • The switch is blocking IPv6 traffic by default

10. Why would a network run IPv4 and IPv6 addressing simultaneously on the same interfaces, a setup often called dual stack?

    • IPv6 requires an IPv4 address to be present before it can operate
    • To migrate gradually while retaining IPv4 applications and devices
    • Dual stack is mandatory on all Cisco IOS devices by default
    • It doubles the available bandwidth on each interface

11. When pinging a link-local IPv6 address such as fe80::1 from a router with multiple interfaces, why does Cisco IOS prompt for an output interface?

    • To select the local link because link-local addresses are not globally unique
    • Ping is not supported for link-local addresses at all
    • It only happens if the router has no default route configured
    • To confirm the destination MAC address manually, since IPv6 ping cannot use Neighbor Discovery for link-local destinations

12. An IPv6 host knows a neighbor is on the local Ethernet link but has no cached MAC address for it. Which exchange resolves the address?

    • ARP request and reply through Ethernet broadcast forwarding
    • DHCPv6 Solicit and Advertise conveying the neighbor MAC address
    • ICMPv6 Neighbor Solicitation and Advertisement
    • DNS AAAA request and response supplying the neighbor MAC address

13. A host receives a valid Router Advertisement with Router Lifetime set to zero. What does that lifetime indicate?

    • Every configured IPv6 address on the host must be deleted immediately
    • It does not offer itself as a default router
    • Every advertised prefix expires, even if it has a nonzero valid lifetime
    • The sender link-local address has become invalid on the attached LAN

14. A service assigns the same IPv6 unicast-format address to interfaces on several nodes. Routing delivers a packet to one selected instance. What addressing method is this?

    • Multicast
    • Broadcast
    • Anycast
    • Link-local flooding

15. Which IPv6 destination reaches all IPv6 nodes on the local link?

    • FF02::1
    • FF02::2
    • ::1
    • FE80::1

16. A host wants to request a Router Advertisement promptly instead of waiting for a periodic advertisement. Which message does it send?

    • DHCPv6 Advertise
    • ARP request
    • ICMPv6 Neighbor Advertisement
    • ICMPv6 Router Solicitation

17. An IPv6 application sends traffic to ::1. Where should that traffic be delivered?

    • Every router on the local link
    • The originating node itself
    • The configured default gateway
    • Every host in the subnet

18. A host sends IPv6 Router Solicitation before it has a usable source address. Which source address can it use?

    • ::1
    • FF02::2
    • ::
    • 2001:db8::ffff

19. A team needs IPv6 addresses for internal communication without expecting global Internet routing. Which prefix contains unique local addresses?

    • FC00::/7
    • FE80::/10
    • FF00::/8
    • 2000::/3