Ipv6 Stateless Auto-Configuration - Brocade Communications Systems FastIron SX 800 Configuration Manual

IPv6 addressing overview
TABLE 29 IPv6 address types (continued)
Address type
A switch automatically configures a link-local unicast address for an interface by using the prefix of FE80::/10 (1111 1110 10) and a
64-bit interface ID. The 128-bit IPv6 address is then subjected to duplicate address detection to ensure that the address is unique on
the link. If desired, you can override this automatically configured address by explicitly configuring an address.
NOTE
Brocade FastIron devices support RFC 2526, which requires that within each subnet, the highest 128 interface identifier values
reserved for assignment as subnet anycast addresses. Thus, if you assign individual IPv6 addresses within a subnet, the second
highest IPv6 address in the subnet does not work.

IPv6 stateless auto-configuration

Brocade routers use the IPv6 stateless autoconfiguration feature to enable a host on a local link to automatically configure its interfaces
with new and globally unique IPv6 addresses associated with its location. The automatic configuration of a host interface is performed
without the use of a server, such as a Dynamic Host Configuration Protocol (DHCP) server, or manual configuration.
The automatic configuration of a host interface works in the following way: a switch on a local link periodically sends switch
advertisement messages containing network-type information, such as the 64-bit prefix of the local link and the default route, to all
nodes on the link. When a host on the link receives the message, it takes the local link prefix from the message and appends a 64-bit
interface ID, thereby automatically configuring its interface. (The 64-bit interface ID is derived from the MAC address of the host's NIC.)
The 128-bit IPv6 address is then subjected to duplicate address detection to ensure that the address is unique on the link.
The duplicate address detection feature verifies that a unicast IPv6 address is unique before it is assigned to a host interface by the
stateless auto configuration feature. Duplicate address detection uses neighbor solicitation messages to verify that a unicast IPv6
address is unique.
NOTE
For the stateless auto configuration feature to work properly, the advertised prefix length in switch advertisement messages
must always be 64 bits.
The IPv6 stateless autoconfiguration feature can also automatically reconfigure a host's interfaces if you change the ISP for the host's
network. (The host's interfaces must be renumbered with the IPv6 prefix of the new ISP.)
The renumbering occurs in the following way: a switch on a local link periodically sends advertisements updated with the prefix of the
new ISP to all nodes on the link. (The advertisements still contain the prefix of the old ISP.) A host can use the addresses created from the
new prefix and the existing addresses created from the old prefix on the link. When you are ready for the host to use the new addresses
only, you can configure the lifetime parameters appropriately using the ipv6 nd prefix-advertisement command. During this transition,
the old prefix is removed from the switch advertisements. At this point, only addresses that contain the new prefix are used on the link.
154
Description Address structure
interface assigned an anycast address must be
configured to recognize the address as an
anycast address.
An anycast address can be assigned to a switch
only.
An anycast address must not be used as the
source address of an IPv6 packet.
FastIron Ethernet Switch Layer 3 Routing
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