IPv6 Address Assignment

5 minutes 5 Questions

IPv6 supports various methods to obtain and assign addresses, either through manual configuration, Stateless Address Autoconfiguration (SLAAC), or Dynamic Host Configuration Protocol for IPv6 (DHCPv6). Manual configuration involves manually assigning IP addresses and other network parameters to devices. SLAAC is an automatic process where hosts generate their own IPv6 addresses by combining a network prefix obtained from a router advertisement with an Interface ID that can be derived from their MAC address or generated randomly. DHCPv6 is responsible for dynamic assignment of addresses and other configurations such as DNS server addresses. Choosing the right address assignment method helps maintain flexibility and efficiency.

IPv6 Address Assignment Guide and Exam Preparation Tips

IPv6 Address Assignment is an important concept due to the expansion of internet-connected devices each requiring a unique IP address. As IPv4 addresses are essentially exhausted, IPv6 promises an almost inexhaustible supply of IP addresses.
The IPv6 Address Assignment is a process by which a network device is assigned a unique IPv6 address.
This is done either dynamically (through DHCPv6) or statically (manually assigned). An IPv6 address is 128 bits long, in comparison to an IPv4 address which is 32 bits long.

Exam Tips: Answering Questions on IPv6 Address Assignment:
- Understand the difference between dynamic and static IPv6 address assignment.
- Make sure you know that a unique IPv6 address is 128 bits long.
- Be aware of how an IPv6 address is structured - it is divided into 8 groups of 4 hexadecimal digits.
- Ensure you understand how subnetting works with IPv6.
- Practice converting binary to hexadecimal and vice versa, as this can often come up in exam questions related to IPv6.
- Understand thoroughly how DHCPv6 works and its impact on IPv6 address assignment.

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Question 1

Your company is transitioning from IPv4 to IPv6. A subnet needs to have 500 devices connected. Which is the most efficient IPv6 prefix to use?

/64 /32 /56 /48

Correct Answer: /64

The most efficient IPv6 prefix to use when connecting 500 devices to a subnet is /64. IPv6 addresses are 128 bits long, and the /64 notation means that the first 64 bits are used for the network address, leaving the other 64 bits for host addresses. This allows for a huge number of unique host addresses well into the trillions, far more than enough for 500 devices. On the contrary, using a /56, /48, or /32 prefix would leave fewer bits for the network address and unnecessarily more bits for host addresses, which is inefficient given the requirement.

Question 2

A network administrator needs to configure an IPv6 address on an interface with EUI-64. The interface's MAC address is 00:11:22:33:44:55. What would be the resulting IPv6 address with the given prefix 2001:0DB8:0001::/64?

2001:0DB8:0001:0000:0011:22FF:3334:4455 2001:0DB8:0001:0000:0211:22FF:3334:4455 2001:0DB8:0001:0000:0011:22FF:FE33:4455 2001:0DB8:0001:0000:0211:22FF:FE33:4455

Correct Answer: 2001:0DB8:0001:0000:0211:22FF:FE33:4455

When generating an IPv6 address using EUI-64, the MAC address is split in half and 'FFFE' is inserted in the middle. The 7th bit of the first byte (which is the 'universe/local' bit) is complemented. The original MAC address is 00:11:22:33:44:55. Following the guidelines, the EUI-64 based part of the address becomes 0211:22FF:FE33:4455. The prefix provides the rest of the address which is 2001:0DB8:0001:0000. Combining them results in the IPv6 address: '2001:0DB8:0001:0000:0211:22FF:FE33:4455'. This is why the correct answer is '2001:0DB8:0001:0000:0211:22FF:FE33:4455'. The other answers are incorrect as they do not comply to the EUI-64 rule to flip the 7th bit, use the correct prefix, or correctly insert 'FFFE'.

Question 3

What is the correct IPv6 multicast address to solicit neighbor information for the IPv6 address 2001:db8::1?

FF02::1:Fdb8:1 FF02::1:FF00:db8 FF02::1:FF00:1 FF02::2:FF00:1

Correct Answer: FF02::1:FF00:1

The correct answer is FF02::1:FF00:1. In IPv6, FF02::1:FF00:0/104 is the prefix used for solicited-node multicast addresses. The last 24 bits of the IPv6 address (2001:db8::1) are appended to the prefix to create the solicited-node multicast address. For the address 2001:db8::1, the last 24 bits are 0:0:1. The Concatenation of FF02::1:FF00:0/104 and 0:0:1 gives FF02::1:FF00:1. The other options, FF02::2:FF00:1, FF02::1:FF00:db8, and FF02::1:Fdb8:1, are not valid as they did not follow the process as described earlier nor the right format.

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