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
   • The interface can still have a valid IPv6 address and link-local address, but the router will not route between IPv6 interfaces
   • 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 eui-64
   • ipv6 address 2001:db8:0:1::1/64 auto
   • ipv6 eui-64 2001:db8:0:1::/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 link-local fe80::1
   • ipv6 address fe80::1/10 local
   • ipv6 local-address fe80::1

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
   • It is automatically created as the interface's link-local address once IPv6 is enabled on that interface
   • 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

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 identify the network, leaving the remaining 64 bits for the interface identifier, which is the standard subnet size for IPv6 LANs
   • 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?

   • No, without unicast routing enabled IPv6 addressing does not function at all
   • Yes, because pinging a directly connected neighbor on the same link does not require the router to forward packets between different interfaces
   • Only if they are also running OSPFv3
   • Only if a DHCPv6 relay is configured between them

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 valid default route or learn a default router through Router Advertisements
   • 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
    • It lets a network transition to IPv6 gradually while existing IPv4 applications and devices continue to work unchanged
    • 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?

    • Link-local addresses are not globally unique, so the router needs to know which local link to send the ping out on
    • Ping is not supported for link-local addresses at all
    • It only happens if the router has no default route configured
    • The router is confirming the destination MAC address before sending

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
    • DHCPv6 Solicit and Advertise
    • ICMPv6 Neighbor Solicitation and Neighbor Advertisement
    • DNS AAAA query and response

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

    • The host must delete every IPv6 address
    • The sender must not be used as a default router on the basis of this advertisement
    • All advertised prefixes have expired
    • The sender's link-local address is invalid