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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Gwendoline Nubila
February 20, 2019 at 6:25 amHi,
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) • Post Author •
February 20, 2019 at 9:09 amI’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 at 8:04 pmAs Joe suggested. I bounced the gi0/0 int on R2 and the interface now shows a Global