IPv6

Question 1

What is IPv6?

Answer 1

• IPv6 addresses use 128 bits (ie 2^128 or 3.4x10^38 IPv6 addresses)
• Uses Hexadecimal System
• 4 hexadecimal digits is referred to as hextet.
• 128 bits = 8 groups of 16 bits/4 Hexadecimal digits ( ie 8 hextets)
• Each hextet is separated by a colon (:)
• IPv6 can be written in either uppercase or lowercase

Question 2

How to simplify IPv6 addresses?

Answer 2

• Leading 0’s (zeros) in any hextet can be omitted
• A double colon (::) can replace any single, contiguous string of one or more hextets consisting of all 0’s
• Double colon (::) can only be used once within an address, otherwise the address will be ambiguous

Question 3

What is a global unicast address?

Answer 3

• Similar to a public IPv4 address, which is internet routable
• Globally unique, no two devices should have identical global unicast address
• Can be static (manual) or dynamic (e.g. DHCPv6)
• Currently, only global unicast addresses with the first three bits of 001 are being assigned.
• The first hextet is 0010 or 0011 => IPv6 address is 2000::/3

Question 4

What is link-local address?

Answer 4

• For communication with other devices on the same subnet (subnet” is also referred to as “link” in IPv6)
• Link-Local Unicast Address is confined to a subnet, not routable beyond the subnet
• Link-local addresses are FE80::/10
• Every IPv6-enabled network interface is required to have a link-local address

Question 5

What is a loopback unicast address?

Answer 5

• Used by a host to send a packet to itself
• Ping an IPv6 loopback address to test the configuration of TCP/IP on the local host
• Cannot be assigned to a physical interface
• The loopback address is all-0s except for the last bit, represented as ::1/128 or just ::1

Question 6

What is an unspecified address?

Answer 6

• Unspecified Address is all-0’s address represented as ::/128 or just ::
• Cannot be assigned to an interface
• Can only used as a source address, when the device does not yet have a permanent IPv6 address, or the source of the packet is irrelevant to the destination

Question 7

What are the migration techniques?

Answer 7

Dual-Stack
* Allows IPv4 and IPv6 to co-exist on the same network
* Devices run both IPv4 and IPv6 protocol stacks simultaneously

Tunneling
* A method of transporting an IPv6 packet over an IPv4 network
* The IPv6 packet is encapsulated inside an IPv4 packet

Translation
* IPv6 packets are translated to IPv4 packets, and vice versa using NAT64 (Network Address Translation 64)
* Through the translation technique, IPv6-only devices can communicate with IPv4-only devices