ZyXEL Communications OLT2406, User Manual

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Chapter 55 IPv6
OLT2406 User’s Guide
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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, see
Interface ID and EUI-64 ) 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 interface is connected to a network with a router and the
ipv6 address autoconfig
command is issued on the OLT, it generates
2
another address which combines its interface ID and
global and subnet information advertised from the router. This is a routable global IP address.
DHCPv6
The Dynamic Host Configuration Protocol for IPv6 (DHCPv6, RFC 3315) is a server-client protocol that
allows a DHCP server to assign and pass IPv6 network addresses, prefixes and other configuration
information to DHCP clients. DHCPv6 servers and clients exchange DHCP messages using UDP.
Each DHCP client and server has a unique DHCP Unique IDentifier (DUID), which is used for identification
when they are exchanging DHCPv6 messages. The DUID is generated from the MAC address, time,
vendor assigned ID and/or the vendor's private enterprise number registered with the IANA. It should not
change over time even after you reboot the device.
Identity Association
An Identity Association (IA) is a collection of addresses assigned to a DHCP client, through which the
server and client can manage a set of related IP addresses. Each IA must be associated with exactly
one interface. The DHCP client uses the IA assigned to an interface to obtain configuration from a DHCP
server for that interface. Each IA consists of a unique IAID and associated IP information.
The IA type is the type of address in the IA. Each IA holds one type of address. IA_NA means an identity
association for non-temporary addresses and IA_TA is an identity association for temporary addresses.
An IA_NA option contains the T1 and T2 fields, but an IA_TA option does not. The DHCPv6 server uses T1
and T2 to control the time at which the client contacts with the server to extend the lifetimes on any
addresses in the IA_NA before the lifetimes expire. After T1, the client sends the server (
S1 ) (from which
the addresses in the IA_NA were obtained) a Renew message. If the time T2 is reached and the server
Table 210
EUI-64 0 2 : 13 : 49 : FF : FE : 12 : 34 : 56
2. In IPv6, all network interfaces can be associated with several addresses.