IPv6

• IPv6 addresses are 128-bit* Layer 3 addresses that are split into eight 16-bit fields called hextets
  • Each field is composed of two hexadecimal that range from 0-F (0-9, A-F)
    • 0 - 15 in decimal
    • 0000 - 1111 in Binary
• Addresses can be shortened by omitting leading 0s and summarizing one group of contiguous 0s as "::"
  • For example, these addresses are the same
    • 2001:0DB8:0000:0000:0001:0000:0000:0001
    • 2001:DB8:0:0:1:0:0:1
    • 2001:DB8:0:0:1::1

IPv6 Multicast Address Scopes - IANA

1. IPv6 addresses use 128-bit addresses split into 8 16-bit fields
   1. Each field contains 4 characters that range from 0-9 and A-F
      1. 
   2. The fields are called hextets, pieces, or quartets (but are technically hexadectets)
2. Addresses can be shortened by removing leading and contiguous Zeros
   1. Only one set of contiguous Zeros can be shorted to "::"
   2. These addresses are the same:
      1. 2001:0DB8:0000:0001:0000:0000:0000:0001
      2. 2001:DB8:0:1:0:0:0:1
      3. 2001:DB8:0:1::1

IPv6 Address types

1. Global Unicast - 2000::/3
   1. Global Unicast addresses are assigned to an individual host and can have global reachability (unless blocked)
   2. Internet authorities assign blocks from the overall 2001::/3 range to organizations
      1. A common assignment for a company is a /48 block, e.g. 2001:2:3::/48
   3. Addresses assigned to individual hosts should use a /64 mask
      1. This splits the address in half; 4 hextets for the network ID, 4 hextets for the host address
      2. 64 host bits = 18.44 Quintillion hosts per subnet
   4. This leaves 16 bits for companies to use for subnetting
      1. 16 bits = 16,535 possible subnets
      2. X:X:X | X | X:X:X:X
      3. Company | Subnet | Host
2. Unique Local - fd00::/8
   1. They are equivalent to IPv4's Private address ranges
      1. They are not globally routable
      2. Uses the range fd00::/8 to assign completely unique addresses to devices
      3. (source: Unique local address - Wikipedia)
         1. The Global ID is a 40-bit Random hexadecimal string
         2. The subnet ID is 16-bits long, and assigned by the administrator
         3. The interface ID is 64-bits long and unique to each device
            1. It can either be stateful (manually configured) or stateless with EUI-64 (automatically generated) with
3. Link Local - FE80::/10
   1. These addresses are required and automatically created, and are only valid on the direct link it is connected to.
   2. It is required for NDP and other

Unicast/Multicast/Anycast Summary

1. Unicast
   1. Global Unicast
      1. 2000::/3
         1. Binary 0010 or 001
   2. Unique Local
      1. FD00::/8
         1. Binary 1111 1101
   3. Link Local
      1. FE80::/10
         1. Binary 1111 1110
2. Anycast
   1. Packets sent to an "Anycast" address are routed to the nearest device with that "Anycast" address associated with it.
      1. e.g., if you had a network with multiple authentication servers across the globe that were peered and used the same anycast address.
3. Multicast
   1. FF00::/8
      1. First two hextets are always 1111 1111 (FF)
      2. Third hextet are flags (currently all set to 0)
      3. fourth hextet defines the scope
         1. 1: Interface-local
         2. 2: Link-local
         3. 5: Site-local
         4. 8: Organization-local
         5. 14: Global scope
      4. The remaining bits are used in the group ID, which identifies the recipient
         1. FF02::1 = All nodes on the local network segment
         2. FF02::2 = all routers on the local network segment

IPv6 Known Prefixes

• Well known Multicast Addresses

Metadata

OSI or TCP/IP Layer

CCNA Exam Topic

#extop-1-8 #extop-1-9

Contributors

Sources

IPv6 - Wikipedia
Unique local address - Wikipedia