Brocade Multi-Service IronWare Routing Configuration Guide (Supporting R05.6.00) - Manual (Page 518)

490 Multi-Service IronWare Routing Configuration Guide
53-1003033-02
IPv6 stateless auto-configuration
The automatic configuration of a host interface works in the following way: a router on a local link
periodically sends router 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 router
advertisement messages must always be 64 bits.
The IPv6 stateless auto-configuration 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 router 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 router
advertisements. At this point, only addresses that contain the new prefix are used on the link.