IPv6: Address Types

To recap on IPv4 address types:

  • Unicast – represents a single host
  • Multicast – represents a group of hosts
  • Broadcasts – represents all hosts

IPv6 Address Types:

  • Unicast – one to one
  • Multicast – one to group
  • Anycast – one to more than one! (More to follow)

Aggregateable Global Unicast Address

  • Or otherwise known as ‘Global Unicast Address‘ 🙂
  • This address is equivalent to the public IPv4 address classes.
  • These addresses are fully routable and can be used for Internet access.
  • The word “aggregateable” refers to the ability to aggregate, or summarize, these addresses to make routing more efficient.
  • The range of IPv6 global unicast addresses is 2000::/3 (any address that begins with 001).

Link Local Address

  • An address that is kept on the local link.
  • Prefix of  Fe80::/10 followed by the interface identifier from the previous post.

More to follow!

Site Local Address (NO LONGER A PART OF IPv6)

These addresses were originally designed to be the equivalent of an IPv4 RFC 1918 private IP address.

Identifying IPv6 Addressing

  • 001 – Global address
  • 1111 1111 – Multicast (FF)
  • 1111 1110 10 – Link Local (FE80)
  • ::x.x.x.x or 0:0:0:0:0:0:x.x.x.x – IPv4-compatible address (Any IPv6 address with the first 96 bits set to zero is an IPv4-compatible address.)

Reserved IPv6 Addresses

IPv4 has the Loopback IP address of 127.0.0.1, the IPv6 equivalent is:

  • IP v6 Loopback: 0000:0000:0000:0000:0000:0000:0000:0001
  • Using Leading Zero Compression Only: 0:0:0:0:0:0:0:1
  • Combining Leading Zero and Zero Compression: ::1

Unspecified IPv6 Address

  • IPv6 Unspecified Address: 0000:0000:0000:0000:0000:0000:0000:0000
  • Using Zero Compression: 0:0:0:0:0:0:0:0, or just ::/128
  • Since the unspecified address is ::/128, it follows that the default route for IPv6 is ::/0

IPv6 to IPv4 Conversion Example

IPv6 Address To Convert: ::D190:4E71

The double-colon is zero compression in action, so now we need to convert the lower 32 bits into decimal.

  • Hex D1 = Decimal 209 (D = 13, 13 * 16 = 280 + how many 1s go into 1? 1! = 209. Hex revision? ;))
  • Hex 90 = Decimal 144
  • Hex 4E = Decimal 78
  • Hex 71 = Decimal 113

The IPv4 address that was embedded into the IPv6 address is 209.144.78.113.

Multicasts

  • IPv4 multicast addresses are Class D addresses with a first octet value of 224 – 239.
  • Any address that begins with “1111 1111”, or “FF” in hex, is a multicast address — the full prefix being FF00::/8.

Local Link Only Notable Addresses

  • FF02::1 — All nodes on the local link
  • FF02::2 — All routers “”
  • FF02::9 — All RIP routers “”
  • FF02::A — All EIGRP routers “”
  • FF02::1:FFzz:zzzz/104 — Solicited-node address. These are used in Neighbor Solicitation messages – more about these very soon. The “z”s are the rightmost 24 bits of the unicast/address of the node.

Anycasts

  • This is a combination of a unicast and multicast.
  • An anycast address is a unicast address assigned to multiple interfaces.
  • A sender transmits an anycast packet in the same manner it would a unicast packet and when the router receives the anycast packet, the router then sends that packet to the closest device with that anycast address.

How IPv6 defines what is ‘closest’?

  • It’s the first learned directly connected neighbor – if there are directly connected neighbors.
  • If that’s not the case, it’s simply the closest neighbor as determined by the routing protocol metric.

More to follow..

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