Dell Brocade DCX, Configuration Manual

Page: 1138 / 1436

1066 BigIron RX Series Configuration Guide
53-1001810-01
IPv6 stateless autoconfiguration
42
IPv6 stateless autoconfiguration
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. .