IPv6 Addresses

IPv6 Addresses

1. IPv6 is designed to be the successor to IPv4. IPv6 has a 128-bit address space, providing for 340 undecillion addresses. (That is the number 340, followed by 36 zeros).

   • IPv4 and IPv6 Coexistence
     • Dual Stack
       • It allows IPv4 and IPv6 to coexist on the same network segment. Dual stack devices run both IPv4 and IPv6 protocol stacks simultaneously.
     • Tunneling
       • It is a method of transporting an IPv6 packet over an IPv4 network. The IPv6 packet is encapsulated inside an IPv4 packet, similar to other types of data.
     • Translation
       • NAT64 allows IPv6-enabled devices to communicate with IPv4-enabled devices using a translation technique similar to NAT for IPv4. An IPv6 packet is translated to an IPv4 packet and vice versa.
   • IPv6 Address Representation
     • IPv6 addresses are 128 bits in length and written as a string of hexadecimal values
       • Every 4 bits is represented by a single hexadecimal digit; for a total of 32 hexadecimal values
         • The set of 4 hexadecimal digits is called hexet
       • Rules
         • Omit Leading 0s
           • 01AB can be represented as 1AB 09F0 can be represented as 9F0 0A00 can be represented as A00 00AB can be represented as AB
         • Omit All 0 Segments
           • A double colon (::) can replace any single, contiguous string of one or more 16-bit segments (hextets) consisting of all 0s
             • The double colon (::) can only be used once within an address
       • Format
     • IPv6 Prefix Length
       • IPv6 uses the prefix length to represent the prefix portion of the address
         • The prefix length can range from 0 to 128. A typical IPv6 prefix length for LANs and most other types of networks is /64
   • IPv6 Address Types
     • Unicast
       • It uniquely identifies an interface on an IPv6-enabled device. A source IPv6 address must be a unicast address.
         • Global unicast address (GUA)
           • 2000::/3
             • Publically routable addresses
         • Link Local
           • FE80::/10
             • Replacement for the APIPA
               • Link-local address enables a device to communicate with other IPv6-enabled devices on the same link and ONLYon that link (subnet).
         • Unique local addresses
           • FC00::/7
             • They are used for local addressing within a site or between a limited number of sites. These addresses should not be routable in the global IPv6 and should not be translated to a global IPv6 address.
     • Multicast
       • FF00::/8
         • Routing protocols use multicast addresses to send there updates
           • There are two types of IPv6 multicast addresses
             • Assigned multicast
               • Addresses that are reserved for predefined groups of devices.
                 • FF02::1 All-nodes multicast group
                   • This is a multicast group that all IPv6-enabled devices join. A packet sent to this group is received and processed by all IPv6 interfaces on the link or network. This has the same effect as a broadcast address in IPv4
                 • FF02::2 All-routers multicast group
                   • This is a multicast group that all IPv6 routers join. A router becomes a member of this group when it is enabled as an IPv6 router with the ipv6 unicast-routing global configuration command. A packet sent to this group is received and processed by all IPv6 routers on the link or network.
             • Solicited node multicast
               • IPv6-enabled devices send ICMPv6 Router Solicitation (RS) messages to the all-routers multicast address. The RS message requests an RA message from the IPv6 router to assist the device in its address configuration
                 • A solicited-node multicast address is mapped to a special Ethernet multicast address. This allows the Ethernet NIC to filter the frame by examining the destination MAC address without sending it to the IPv6 process to see if the device is the intended target of the IPv6 packet.
     • Anycast
       • Anycast packet is delivered to only one device, the one closest to it based on the routing process used. That’s why it is called “one to nearest”. Also you apply a single address to more than one host.
     • other addresses
       • ::1 loopback
       • ::/128 Unspecified address

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