ICND1 IPv4 and IPv6 3 — Questions and Answers
Question 1: Which IPv6 transition mechanism encapsulates IPv6 packets inside IPv4 packets to traverse IPv4 networks?
- NAT64
- Dual-stack
- 6to4 tunneling (Correct answer)
- DHCPv6
Correct answer: 6to4 tunneling
6to4 tunneling automatically encapsulates IPv6 traffic in IPv4 packets (protocol 41) to cross IPv4-only infrastructure.
Question 2: What is the subnet mask in dotted-decimal notation for a /20 prefix?
- 255.255.240.0 (Correct answer)
- 255.255.248.0
- 255.255.252.0
- 255.255.224.0
Correct answer: 255.255.240.0
A /20 means 20 bits are set to 1: the first two octets are 255.255, and the third octet has 4 bits set (11110000) = 240.
Question 3: Which type of IPv6 address is used to identify a set of interfaces, delivering the packet to the nearest one?
- Unicast
- Multicast
- Anycast (Correct answer)
- Broadcast
Correct answer: Anycast
Anycast addresses are assigned to multiple interfaces; routing delivers packets to the topologically nearest interface in that set.
Question 4: A router interface is configured with IP address 10.1.1.1/30. How many other hosts can be on this subnet?
- 0
- 1 (Correct answer)
- 2
- 6
Correct answer: 1
A /30 subnet has 4 addresses total; network=.0, broadcast=.3, so only .1 and .2 are usable — meaning one other host can share this subnet.
Question 5: What is the purpose of the IPv6 Neighbor Discovery Protocol (NDP)?
- Assign IPv6 addresses via a server
- Replace ARP and provide router/prefix discovery (Correct answer)
- Encrypt IPv6 traffic between hosts
- Translate IPv6 to IPv4 addresses
Correct answer: Replace ARP and provide router/prefix discovery
NDP uses ICMPv6 messages to perform address resolution (replacing ARP), router discovery, and prefix advertisement in IPv6 networks.
Question 6: Which private IPv4 address range is defined by RFC 1918 for Class B networks?
- 10.0.0.0 – 10.255.255.255
- 172.16.0.0 – 172.31.255.255 (Correct answer)
- 192.168.0.0 – 192.168.255.255
- 169.254.0.0 – 169.254.255.255
Correct answer: 172.16.0.0 – 172.31.255.255
RFC 1918 defines 172.16.0.0/12 (172.16.0.0 through 172.31.255.255) as the private Class B range.
Question 7: An IPv6 address is written as 2001:0DB8:0000:0000:0000:0000:0000:0001. What is its compressed form?
- 2001:DB8::1 (Correct answer)
- 2001:DB8:0:0:0:0:0:1
- 2001:0DB8::0001
- 2001:DB8:0::1
Correct answer: 2001:DB8::1
Leading zeros in each group are removed and the longest consecutive run of all-zero groups is replaced with :: giving 2001:DB8::1.
ICND1 IPv4 and IPv6 3
Which IPv6 transition mechanism encapsulates IPv6 packets inside IPv4 packets to traverse IPv4 networks?