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Ipv6 Address Distribution:

IPv6 addresses are 128-bit identifiers for interfaces and sets ofinterfaces. There are three types of addresses:Unicast:An identifier for a single interface. A packet sent to a unicast address is delivered to the interface

identified by that address.

Anycast:An identifier for a set of interfaces (typically belonging to different nodes). A packet sent to an

anycast address is delivered to one of the interfaces identified by that address (the "nearest" one,according to the routing protocols measure of distance).

Multicast:An identifier for a set of interfaces (typically belonging to different nodes). A packet sent to a multicastaddress is delivered to all interfaces identified by that address.

Unicast address format :

1)Aggregatable Global Unicast Addresses :

TLA ID Top-Level Aggregation Identifier. The size of this field is 13 bits. The TLA ID identifiesthe highest level in the routing hierarchy

Res Bits that are reserved for future use in expanding the size of either the TLA ID or the NLA ID(defined next). The size of this field is 8 bits.

NLA ID Next-Level Aggregation Identifier. The size of this field is 24 bits. The NLA ID allows anISP to create multiple levels of addressing hierarchy within its network to both organize addressing androuting for downstream ISPs and identify organization sites.

SLA ID Site-Level Aggregation Identifier. The SLA ID is used by an individual organization toidentify subnets within its site. The size of this field is 16 bits. The organization can use these 16 bits

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within its site to create 65,536 subnets or create multiple levels of addressing hierarchy .

Interface ID Indicates the interface on a specific subnet. The size of this field is 64 bits. Theinterface ID in IPv6 is equivalent to the node ID or host ID in Ipv4.

2)Link-Local Addresses :

Link-local addresses, identified by the FP of 1111 1110 10, are used by nodes when communicatingwith neighboring nodes on the same link. For example, on a single link IPv6 network with no router,link-local addresses are used to communicate between hosts on the link .

3)Site-Local Addresses :

Site-local addresses, identified by the FP of 1111 1110 11, are equivalent to the IPv4 private address

space (10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16). For example, private intranets that do not have adirect, routed connection to the IPv6 Internet can use site-local addresses without conflicting withglobal addresses. Site-local addresses are not reachable from other sites, and routers must not forwardsite-local traffic outside the site. Site-local addresses can be used in addition to global addresses.

4)Special IPv6 Addresses :

Unspecified address

The unspecified address (0:0:0:0:0:0:0:0 or ::) is used only to indicate the absence of an address. It isequivalent to the IPv4 unspecified address of 0.0.0.0. The unspecified address is typically used as asource address when a unique address has not yet been determined. The unspecified address is neverassigned to an interface or used as a destination address

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Loopback address

The loopback address (0:0:0:0:0:0:0:1 or ::1) is used to identify a loopback interface, enabling a nodeto send packets to itself. It is equivalent to the IPv4 loopback address of 127.0.0.1. Packets addressed tothe loopback address must never be sent on a link or forwarded by an IPv6 router.

MULTICAST IPV6 ADDRESSES :

In IPv6, multicast traffic operates in the same way that it does in IPv4. Arbitrarily located IPv6 nodescan listen for multicast traffic on an arbitrary IPv6 multicast address. IPv6 nodes can listen to multiplemulticast addresses at the same time. Nodes can join or leave a multicast group at any time. IPv6multicast addresses have the FP of 1111 1111. Therefore, an IPv6 multicast address always begins withFF. Multicast addresses cannot be used as source addresses or as intermediate destinations in a Routingheader. Beyond the FP, multicast addresses include additional structure to identify flags, their scope,

and the multicast group .

Flags Indicates flags set on the multicast address. The size of this field is 4 bits.

The high-order 3 flags are reserved, and must be initialized to 0. T = 0 indicates a permanently-assigned ("well-known") multicast address, assigned by the global internet numbering authority. T = 1indicates a non-permanently-assigned ("transient") multicast address.

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Scope Indicates the scope of the IPv6 network for which the multicast traffic is intended to bedelivered. The size of this field is 4 bits. In addition to information provided by multicast routingprotocols, routers use the multicast scope to determine whether multicast traffic can be forwarded. Forexample, traffic with the multicast address of FF02::2 has a link-local scope. An IPv6 router never

forwards this traffic beyond the local link.

Group ID Identifies the multicast group and is unique within the scope. The size of this field is 112bits. Permanently assigned group IDs are independent of the scope. Transient group IDs are relevantonly to a specific scope.

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