Introduction
In IPV4, there are 3 communications types
- –Unicast – This is a one-to-one communication model (client sending to server)
- –Multi-cast – One-to-many communication model (Streaming to subscribed group, YouTube, streaming services are examples.)
- –Broadcast -One-to-all (Television signals sent from a public network to viewers across the country/globe are a simple example of broadcast transmission. For computer networks, broadcast transmission is generally used on LANs (Local Area Networks).)
Multi-cast has its own address range and it starts where class c addressing stops. Class A(0 -126) | Class B(128 -191) Class C(192 -223) MULTI-CAST (starts at 224)
Also in IPV6, there are 3 communication types
- –Unicast – This is a one-to-one communication model (client sending to server)
- –Multi-cast – One-to-many communication model (Streaming to subscribed group, YouTube, streaming services are examples.)
- –Anycast -One-to-closest (A packet sent to an anycast address is delivered to (the nearest interface), according to the routing protocols’ measure of distance.)
Types of IPV6 Addresses
- Link Local addresses
- Global Scope addresses
- Unique /Site local addresses.
(1) Link local starts with fe80::(This is APIPA in IPV4)
Link local addresses start with FE80 followed by 54 bits of zeros where FE80 is 16 bit + 54 bits = 64bits which forms the network part of the ip address. fe08::/64. The remaining portion of the IPV6 address which is the host portion is made up of the mac-address (which is 48bits) of the NIC, falling short of 16bits to make the 64bits for the host. Remember, 64bits for the network portion and another 64bits for the host portion, making 128bits ipv6 address. Link local is Not Routed internally or externally. This is automatically generated by the computer and its used for local. These are meant to be used inside an internal network, and again they are not routed on the Internet. It is equivalent to the IPv4 address 169.254.0.0/16 which is allocated on an IPv4 network when no DHCP server is found. Link Local addresses are self assigned i.e. they do not require a DHCP server. A link local address is required on every IP6 interface even if no routing is present. It is automatically assigned by the router as soon as the IPV6 is enabled or turned on.
Modified EUI 64
EUI-64 (extended unique identifier) is a mechanism for auto generating the “host” part of a IPv6 address and is created by inserting the hex number FFFE in the middle of the MAC address of the network card. Also, the 7th bit in the first byte is flipped to a binary 1. The interface ID created this way is known as the modified extended unique identifier 64 (EUI-64).
Here are the rules that a router uses to create the interface ID:
- Split the MAC address in two halves.
- Insert FFFE in between the two, making the interface ID. (6 hex digits each).
- Invert the seventh bit of the interface ID.
Example
if the MAC address of a network card is 0019.d1bb.dcf3, the interface ID would be 0219.d1ff.ff22.dcf3.
Why is that so? Well, the router will first flip the seventh bit from 0 to 1. MAC addresses are in hex format. So, first convert to binary and the binary format of the MAC address looks like this:
- First, the router will insert FFFE in the middle of the address listed above: hex – 02BBCCFFFEDD1122
- hex – binary =0019.d1FF.FEbb.dcf3 = 0000 0000 0001 1001. 1101 0001 1111 1111. 1111 1111 0010 0010.1101 1100 1111 0011 (***See Hex to Binary table conversion here***)
- The router will flip the seventh bit: 0000 0010 0001 1001. 1101 0001 1111 1111. 1111 1111 0010 0010.1101 1100 1111 0011
- This will result in the following hexadecimal address: hex – 0219.d1ff.ff22.dcf3
So, the interface ID will be 0219.d1ff.ff22.dcf3 (This represents the host portion of the link local address)
The Link local address will be fe80::0219.d1ff.ff22.dcf3
NOTE: Microsoft decided not to use the EUI-64, so you will not the see the FFFE portion as expected on your pc because Microsoft decided to adopt the RFC 4941 known as the privacy extension to IPV6, which took the Mac-address and hashed it (encryption), which generates what you eventually see as the link local and with this, you can not go backward to determine the mac-address. Just a security measure from Microsoft. Cisco on the other hand use the EUI-64 to generate the address.
(2) Global unicast Addresses
Global Unicast addresses are routable on the internet and start with (2001:)
These addresses are the equivalent of the public addresses of IPv4 networks. The Internet authorities IANA is responsible for allocating the IPv6 global unicast address space to ISPs who in turn allocate them to their customers. They have unlimited scope. Currently, the range of allocated IPv6 addresses starts from prefix 2000::/3.
The allocation process is:
The IANA is allocating out of 2000::/3 for initial IPv6 unicast use
Each registry gets a /12 prefix from the IANA
Registry allocates a /32 prefix (or larger) to an IPv6 ISP
Policy is that an ISP allocates a /48 prefix to each end
customer.
The global prefix =is whatever the carrier decides to set it to and so, your subnet ID =64-n, where n is 48bits or less
Example:
- if you are given a /48bit ip address,
- it means, 64-48
- 16bits.
- It means, you have 16bits that you can play around with and change to create your subnets within the global address. The subnet ID becomes your playground and you cannot go beyond . Whatever the global prefix is minus it from the 64bits and that give you your subnet ID.
(3) Unique local starts with fd00::/8 (Private IP Addresses)
Unique Local are meant to be used inside an internal network. They are routed on the Internal network but not routed on the Internet. They are equivalent to the IPv4 private addresses (10.0.0.0/8), (172.16.0.0/12) and (192.168.0.0/16). The address space is divided into two /8 spaces:
- fc00::/8 for globally assigned addressing, and
- fd00::/8 for locally assigned addressing.
For manual assignment by an organization, use the fd00 prefix. Scope Internal Network or VPN internally routable, but Not routed on Internet
Unique local unicast addresses use the prefix of FD00::/8 and were designed to replace site-local addresses, which are being deprecated.
(4) Anycast
The anycast IPv6 addresses might seem like a new type of address, but the concept is not new. Anycast addresses can be thought of as a cross between unicast and multicast addresses. While the unicast traffic sends information to one address and the multicast traffic sends information to every address in the group, the anycast traffic sends information to any one address of the group. The trick is which address of the group to send information to. The most logical and efficient answer is the nearest or the closet address. Similar to multicast where the nodes will join the multicast group, the anycast nodes share the same anycast address. The data will be sent to a node within the anycast group. This node is the nearest to the sender.
(5) Multicast starts with fe00::
Multicast IPv6 addresses begin with the hexadecimal digits (FF).
IPv6 multicast addresses are commonly used in a similar way to IPv4 multicast addresses – routing protocols and other overhead protocols. IPv6 multicast addresses are defined for a group of networking devices. Data packets sent to a multicast address are sent to the entire group of networking devices such as a group of routers running the same routing protocol. Multicast addresses all start with the prefix FF00::/8. The next group of characters in the IPv6 multicast address (the second octet) are called the scope. The scope bits are used to identify which ISP should carry the data traffic.
IPV6 Special Addresses
- :: /128 =Unspecified address (Simply all zeros)
- :: /0 = Default route. IPV4’s default route is 0.0.0.0 with subnet 0.0.0.0. its the same concept for ipv6.
- ::1 /128 = Loopback address. IPV$ loopback address is 127.0.0.1 to 127.255.255.255. in IPV6, only 0:0:0:0:0:0:0:1 /128 represents the loopback.