I setup IPv6 in my Ubuntu 12.04 on eth0 using command

ifconfig eth0 inet6 add 2001:db8:fedc:cdef::1/64

but when i try to ping eth0 itself using

ping6 2001:db8:fedc:cdef::1

it always gives

PING 2001:db8:fedc:cdef:0:0:0:1(2001:db8:fedc:cdef::1)  56 data bytes
 From ::1 icmp_seq=1 Destination unreachable: Address unreachable
 From ::1 icmp_seq=2 Destination unreachable: Address unreachable
 From ::1 icmp_seq=3 Destination unreachable: Address unreachable

I think that it automatically is pinging from ::1 to `2001:db8:fedc:cdef::1


ip addr show dev eth0

it gives

2: eth0:<NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN qlen 1000
link/ether 00:1b:38:a1:a2:50 brd ff:ff:ff:ff:ff:ff
inet6 2001:db8:fedc:cdef::1/64 scope global tentative 
   valid_lft forever preferred_lft forever


ip -6 route

it gives

2001:db8:fedc:cdef::/64 dev eth0  proto kernel  metric 256 
fe80::/64 dev eth0  proto kernel  metric 256 


ip6tables -L

it gives

Chain INPUT (policy ACCEPT)
target     prot opt source               destination         

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination   


ip6tables -F
it gives nothing.

Please help how to solve this.
this may have clue for someone


ip -6 route get 2001:db8:fedc:cdef::1


2001:db8:fedc:cdef::1 from :: via 2001:db8:fedc:cdef::1 dev eth0  src ::1  metric 0 

why it has src ::1 ?

  • I cannot reproduce this. My guess would be that your eth0 interface is down. Please update your question with the output of ip addr show dev eth0 and maybe ip -6 route. – Celada Feb 15 '13 at 15:05
  • Also check your ip6tables (run ip6tables -L). You may need to run ip6tables -F. – Jeremy Visser Feb 16 '13 at 4:26
  • @celada My eth0 interface is not down. i updated my question with required content. – Sumit Kamboj Feb 18 '13 at 18:05
  • 1
    NO-CARRIER is a little suspect though. – Steve-o Feb 18 '13 at 18:31
  • @Steve-o please how to solve this. – Sumit Kamboj Feb 19 '13 at 18:38

The IPv6 address is showing as tentative because duplicate address detection can't be completed. And the reason that can't happen is because you have no physical Ethernet connection (the link shows NO-CARRIER).

To resolve the issue, connect your Ethernet cable.

  • You are right. IPv6 address does work until you plug ethernet cable. Thanks to alll for reply. – Sumit Kamboj Oct 17 '14 at 9:27

IPv6 address range 2001:db8::/32 is reserved for documentation only and packets with these addresses should never exist on a network. All routers must discard packet with such addresses. Use another address range, e.g. Unique LocaL Addresses fd00::/8 (RFC 4193). If you want to get connection to internet, ask your provider for an ipv6-address-prefix.

  • 1
    This answer is unhelpful and not relevant to the question. Perhaps the O.P. was using the documentation prefix intentionally to make it suitable for posting on the internet? Give the benefit of the doubt here. – Jeremy Visser Mar 6 '13 at 12:39

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