ICND1 IPv4 and IPv6 5 — Questions and Answers
Question 1: Which IPv6 address type is functionally equivalent to an IPv4 private address and is routable only within an organization (not on the internet)?
- Link-local (FE80::/10)
- Unique local (FC00::/7) (Correct answer)
- Global unicast (2000::/3)
- Multicast (FF00::/8)
Correct answer: Unique local (FC00::/7)
Unique local addresses (FC00::/7, typically FD00::/8) are the IPv6 equivalent of RFC 1918 private addresses — routable within a site but not on the global internet.
Question 2: What is the broadcast address of the subnet 10.0.0.0/8?
- 10.255.255.254
- 10.255.255.255 (Correct answer)
- 10.0.0.255
- 10.128.0.0
Correct answer: 10.255.255.255
For 10.0.0.0/8, all 24 host bits set to 1 gives a broadcast address of 10.255.255.255.
Question 3: A Cisco router shows 'show ipv6 interface brief' and displays 'FE80::1' under GigabitEthernet0/0. What kind of address is this?
- Global unicast assigned by DHCP
- Link-local address auto-configured on the interface (Correct answer)
- Loopback address for testing
- Anycast address shared with other routers
Correct answer: Link-local address auto-configured on the interface
FE80::/10 addresses are link-local and are automatically configured on every IPv6-enabled interface without needing global routing.
Question 4: Which protocol does IPv6 use instead of IGMP for multicast group management?
- NDP
- MLD (Multicast Listener Discovery) (Correct answer)
- PIM
- OSPFv3
Correct answer: MLD (Multicast Listener Discovery)
Multicast Listener Discovery (MLD) is the IPv6 equivalent of IGMP and is used by hosts to join or leave multicast groups.
Question 5: How many IPv4 addresses does a /23 subnet contain in total?
- 256
- 512 (Correct answer)
- 1024
- 2048
Correct answer: 512
A /23 has 9 host bits, so 2^9 = 512 total addresses (510 usable hosts).
Question 6: Which Cisco IOS command enables IPv6 routing on a router?
- ip routing
- ipv6 unicast-routing (Correct answer)
- ipv6 enable
- ip ipv6 forward
Correct answer: ipv6 unicast-routing
The global configuration command 'ipv6 unicast-routing' enables the router to forward IPv6 packets between interfaces.
Question 7: What is the network address and prefix length for an IP address of 172.20.15.130 with a subnet mask of 255.255.255.128?
- 172.20.15.0/25
- 172.20.15.128/25 (Correct answer)
- 172.20.15.128/26
- 172.20.15.0/26
Correct answer: 172.20.15.128/25
255.255.255.128 is /25 (block of 128); 130 falls in the second block starting at .128, so the network address is 172.20.15.128/25.
ICND1 IPv4 and IPv6 5
Which IPv6 address type is functionally equivalent to an IPv4 private address and is routable only within an organization (not on the internet)?