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IPv6

IPv6 . State-less Auto-configuration. 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.

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IPv6

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  1. IPv6 State-less Auto-configuration

  2. 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 Autoconfiguration

  3. Autoconfigured Address States • There can be 5 states • 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 Autoconfiguration

  4. Autoconfigured Address States – contd. • 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 Autoconfiguration

  5. Autoconfigured Address States – contd. • 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. • 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. • 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 Autoconfiguration

  6. 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 Autoconfiguration

  7. 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 Autoconfiguration

  8. 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 Autoconfiguration

  9. 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 Autoconfiguration

  10. 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 Autoconfiguration

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

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

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