Addressing Standards
The IANA has allocated several ranges of IPv6 addresses for altered purposes. RFC 4294 defines these rules, afterlight the beforehand RFC 3513 document. This certificate defines three accepted classes of addressesUnicast, Multicast and Anycast. In addition, the accepted defines several altered types of Unicast address. As with IPv4, these altered abode types are abnormally articular by the aboriginal few $.25 of the address.
A unicast abode identifies a distinct interface on a device. This is about the aforementioned as in IPv4 addressing, except that sometimes IPv4 addresses can represent two or added interfaces or accessories through mechanisms like NAT and HSRP.
A multicast abode in IPv6 functions absolutely the aforementioned as in IPv4. Amuse accredit to Chapter 23 for added advice about IPv4 multicast protocols.
Anycast is a almost new abstraction with IPv6, although it was proposed as an addendum for IPv4 and is absolutely acclimated in a bound way with the archetype of an IPv4 Anycast Rendezvous Point for multicast cartage (please accredit to Chapter 23 for an example). An anycast abode can represent several altered interfaces or devices, any one of which may accept the packet. There are IPv4 mechanisms for accomplishing this effect. The basic IP abode in VRRP and HSRP is finer an anycast as any of the accessories in the accumulation can handle the packet. The VRRP or HSRP agreement artlessly elects which accessory is currently administration a accurate abode on account of the group. Similarly, amount acclimation accessories are generally acclimated to angle in advanced of a basin of servers, accepting packets for a distinct destination abode and distributing the access amid the pool.
With IPv6, though, this abstraction is formalized. Normally bodies say that the "closest" anycast accessory will respond, but as the examples in the antecedent branch suggest, there are abounding added added adult applications for this anycast abstraction than alone award the abutting of a accumulation of devices.
Perhaps the better change is that there is no advertisement in IPv6.
The altered types of abode are defined by the aboriginal several bits, as apparent in Table 25-1.