IPv6 State-less Auto-configuration

IPv6 Stateless Autoconfiguration2 Stateless Autoconfiguration Overview One of the most useful aspects of IPv6 is its ability to automatically configure itself, even without the use of a stateful configuration protocol such as DHCPv6. By default, an IPv6 host can configure a link-local address for each interface. By using router discovery, a host can also determine the addresses of routers, other configuration parameters, additional addresses, and on-link prefixes. Included in the Router Advertisement message is an indication of whether a stateful address configuration protocol should be used. Address autoconfiguration can only be performed on multicast- capable interfaces. Address autoconfiguration is described in RFC 2462.

IPv6 Stateless Autoconfiguration3 Autoconfigured Address States There can be 5 states 1. Tentative The address is in the process of being verified as unique. Verification is done through DAD. A node cannot receive unicast traffic to a tentative address. It can, however, receive and process multicast Neighbor Advertisement messages sent in response to the Neighbor Solicitation message that has been sent during DAD.

IPv6 Stateless Autoconfiguration4 Autoconfigured Address States – contd. 2. Valid An address for which uniqueness has been verified and from which unicast traffic can be sent and received. It covers both the preferred and deprecated states. The amount of time that an address remains in the tentative and valid states is determined by the Valid Lifetime field in the Prefix Information option of a Router Advertisement message. The valid lifetime must be > = preferred lifetime. A valid address is either preferred or deprecated.

IPv6 Stateless Autoconfiguration5 Autoconfigured Address States – contd. 3. Preferred A node can send and receive unicast traffic to and from a preferred address. The period of time that an address can remain in the tentative and preferred states is determined by the Preferred Lifetime field in the Prefix Information option of a Router Advertisement message. 4. Deprecated An address that is still valid, but its use is discouraged for new communication. Existing communication sessions can still use a deprecated address. A node can send and receive unicast traffic to and from a deprecated address. 5. Invalid An address for which a node can no longer send or receive unicast traffic. An address enters the invalid state after the valid lifetime expires.

IPv6 Stateless Autoconfiguration6 The states and lifetimes for an autoconfigured address With the exception of autoconfiguration for link-local addresses, address autoconfiguration is only specified for hosts. Routers must obtain address and configuration parameters through another means, such as manual configuration.

IPv6 Stateless Autoconfiguration7 Stateless Autoconfiguration Phase 1: An identifies is generated, supposedly on the link by using the EUI-48 MAC address Phase 2: A tentative address is built: by following mechanism Prefix advertisement Router advertisement and Router solicitation Phase 3: The uniqueness of this address on the link is verified By Duplicate Address Detection (DAD) mechanism Phase 4: If unique, the address from phase 2 is assigned to the interface.

IPv6 Stateless Autoconfiguration8 Stateless Autoconfiguration Prefix Advertisement Advertises prefixes & parameters on a local link. This information is used by IPv6 nodes to configure their IPv6 addresses DAD Ensures that each IPv6 address configured on an interface using stateless auto configuration is unique Prefix renumbering Advertises modified prefixes or new prefixes and parameters the local link to renumber a prefix already advertised.

IPv6 Stateless Autoconfiguration9 Stateless Autoconfiguration Process Generate a link local address Verify this tentative address Is ok. Use a neighbor solicitation with the tentative address as the target. ICMP type 135 If the address is in use a neighbor advertisement Message will be returned. ICMP type 136 If no response Assign the address to the Interface. At this point the Node can communicate On-link. Fail and go to manual Configuration or choose A different interface token

IPv6 Stateless Autoconfiguration10 Stateless Autoconfiguration Process Assign address to Interface. Node joins the All Routers Multicast group. FF02::1 Sends out a router Solicitation message to That group. ICMP type 133 Router responds with a Router advertisement. ICMP type 134

IPv6 Stateless Autoconfiguration11 Stateless Autoconfiguration Process Look at the managed address configuration" flag If M= 0 proceed with Stateless configuration If M=1 stop and Do statefull configuration. Look at "other stateful configuration" flag If O = 0 finish If O= 1 use statefull Configuration for other information

IPv6 Stateless Autoconfiguration12 Stateles Autoconfiguration Displaying Prefix advertisement parameters In Cisco: valid lifetime = 30 days & preferred lifetime = 7 days by default