ZyXEL Communications ZyWall ATP series User Manual page 209

Link-local Address
A link-local address uniquely identifies a device on the local network (the LAN). It is similar to a "private IP
address" in IPv4. You can have the same link-local address on multiple interfaces on a device. A link-
local unicast address has a predefined prefix of fe80::/10. The link-local unicast address format is as
follows.
Table 89 Link-local Unicast Address Format
1111 1110 10 0
10 bits 54 bits
Subnet Masking
Both an IPv6 address and IPv6 subnet mask compose of 128-bit binary digits, which are divided into
eight 16-bit blocks and written in hexadecimal notation. Hexadecimal uses four bits for each character
(1 ~ 10, A ~ F). Each block's 16 bits are then represented by four hexadecimal characters. For example,
FFFF:FFFF:FFFF:FFFF:FC00:0000:0000:0000.
Stateless Autoconfiguration
With stateless autoconfiguration in IPv6, addresses can be uniquely and automatically generated.
Unlike DHCPv6 (Dynamic Host Configuration Protocol version six) which is used in IPv6 stateful
autoconfiguration, the owner and status of addresses don't need to be maintained by a DHCP server.
Every IPv6 device is able to generate its own and unique IP address automatically when IPv6 is initiated
on its interface. It combines the prefix and the interface ID (generated from its own Ethernet MAC
address) to form a complete IPv6 address.
When IPv6 is enabled on a device, its interface automatically generates a link-local address (beginning
with fe80).
When the Zyxel Device's WAN interface is connected to an ISP with a router and the Zyxel Device is set
to automatically obtain an IPv6 network prefix from the router for the interface, it generates another
address which combines its interface ID and global and subnet information advertised from the router.
(In IPv6, all network interfaces can be associated with several addresses.) This is a routable global IP
address.
Prefix Delegation
Prefix delegation enables an IPv6 router (the Zyxel Device) to use the IPv6 prefix (network address)
received from the ISP (or a connected uplink router) for its LAN. The Zyxel Device uses the received IPv6
prefix (for example, 2001:db2::/48) to generate its LAN IP address. Through sending Router
Advertisements (RAs) regularly by multicast, the router passes the IPv6 prefix information to its LAN hosts.
The hosts then can use the prefix to generate their IPv6 addresses.
IPv6 Router Advertisement
An IPv6 router sends router advertisement messages periodically to advertise its presence and other
parameters to the hosts in the same network.
Chapter 9 Interfaces
Interface ID
64 bits
ZyWALL ATP Series User's Guide
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