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CCNA 1.14: Configure and verify IPv6 Stateless Address Auto Configuration

Overview:

IPv6 Stateless address autoconfiguration is similar to DHCP in IPv4.  Routers running IPv6 can give the network prefix and gateway address to clients looking for an IPv6 address.  The device needs a global IPv6 address to be able to connect to the network (and internet).  IPv6 stateless autoconfiguration is a way for a device to automatically generate global IPv6 addresses without the need for manual configuration or help of a server, such as a Dynamic Host Configuration Protocol (DHCP) server.

 

Study Notes:

  • A node can automatically configure its own IPv6 address by appending its 64-bit interface identifier to the 64-bit prefix it receives from a Router Advertisement (RA) message
  • The 128-bit IPv6 address is then subjected to duplicate address detection (DAD) to ensure uniqueness
  • If the prefixes advertised in the RA messages are globally unique, then the IPv6 addresses configured by the node are also guaranteed to be globally unique.
  • Device solicitation messages, which have a value of 133 in the Type field of the ICMP packet header, are sent by hosts at system startup so that the host can immediately autoconfigure without needing to wait for the next scheduled RA message.
  • So what happens if there is a duplicate?  That’s beyond the CCNA, but normally it will disable the interface for IPv6.  There are other cases you can read about in RFC4862 if you like.

 

PacketTracer Lab: CCNA-1.14-Configure-and-verify-IPv6-Stateless-Address-Auto-Configuration.pkt

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Links:

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipv6/configuration/15-2mt/ip6-15-2mt-book/ip6-statlss-auto.html

 


   3 Comments


  1. Gwendoline Nubila
      February 20, 2019

    Hi,

    I completed the lab but obtained a link local address for R2 instead of a global address.Why?

    See verification commands below:

    R1#sh ipv6 int g0/0
    GigabitEthernet0/0 is up, line protocol is up
    IPv6 is enabled, link-local address is FE80::20C:CFFF:FEDD:D001
    No Virtual link-local address(es):
    Global unicast address(es):
    2001:3D81:90BC:1:20C:CFFF:FEDD:D001, subnet is 2001:3D81:90BC:1::/64 [EUI]
    Joined group address(es):
    FF02::1
    FF02::1:FFDD:D001
    MTU is 1500 bytes
    ICMP error messages limited to one every 100 milliseconds
    ICMP redirects are enabled
    ICMP unreachables are sent
    ND DAD is enabled, number of DAD attempts: 1
    ND reachable time is 30000 milliseconds

    R2:
    R2#sh ipv6 int g0/0
    GigabitEthernet0/0 is up, line protocol is up
    IPv6 is enabled, link-local address is FE80::201:42FF:FE82:7801
    No Virtual link-local address(es):
    No global unicast address is configured
    Joined group address(es):
    FF02::1
    FF02::1:FF82:7801
    MTU is 1500 bytes
    ICMP error messages limited to one every 100 milliseconds
    ICMP redirects are enabled
    ICMP unreachables are sent
    ND DAD is enabled, number of DAD attempts: 1
    ND reachable time is 30000 milliseconds

    • Joe Barger (CCNP/CCDP)
        February 20, 2019

      I’m unable to replicate that. If it continues for you, try completing the lab and then shutting and no shutting int g0/0 on R2. That should generate the global address.

    • MOISES CARABALLO
        June 23, 2019

      As Joe suggested. I bounced the gi0/0 int on R2 and the interface now shows a Global

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