Hi, I am using 12.04 and that particular sequence appears to be expected behavior due to duplicate address detection in ipv6 leading to the ipv6 address being tentative. I see similar behavior on an ethernet port which has never physically been connected to anything.
Before attaching anything to the bridge, it has NO-CARRIER and tentative ipv6 address, ping does not work: $ ip addr show br0 26: br0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN link/ether 00:16:3e:ff:00:01 brd ff:ff:ff:ff:ff:ff inet6 2605:2700:0:18::1/64 scope global tentative valid_lft forever preferred_lft forever After attaching something which is itself up: $ ip addr show br0 26: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP link/ether 00:16:3e:ff:00:01 brd ff:ff:ff:ff:ff:ff inet6 2605:2700:0:18::1/64 scope global valid_lft forever preferred_lft forever inet6 fe80::216:3eff:feff:1/64 scope link valid_lft forever preferred_lft forever ping works at this point. Furthermore, after removing the interface, NO-CARRIER is back but the address is still no longer tentative and is still pingable: $ ip addr show br0 26: br0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN link/ether 00:16:3e:ff:00:01 brd ff:ff:ff:ff:ff:ff inet6 2605:2700:0:18::1/64 scope global valid_lft forever preferred_lft forever inet6 fe80::216:3eff:feff:1/64 scope link valid_lft forever preferred_lft forever $ ping6 -c1 2605:2700:0:18::1 PING 2605:2700:0:18::1(2605:2700:0:18::1) 56 data bytes 64 bytes from 2605:2700:0:18::1: icmp_seq=1 ttl=64 time=0.047 ms With 3.5.0-43-generic, I set net.ipv6.conf.all.dad_transmits and net.ipv6.conf.all.accept_dad to 0 and that doesn't cause the addresses to no longer be tentative. It seems like redhat may have had a similar bug https://bugzilla.redhat.com/show_bug.cgi?id=709271 but it is not clear what they did to fix it. I have not yet tried more recent kernels to see if the problem is fixed there. ** Bug watch added: Red Hat Bugzilla #709271 https://bugzilla.redhat.com/show_bug.cgi?id=709271 -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/894272 Title: ipv6 broken for bridge Status in “linux” package in Ubuntu: Triaged Bug description: ipv6 seems to be broken on bridges in oneiric: root@office:/home/markus# uname -a Linux office 3.0.0-12-virtual #20-Ubuntu SMP Fri Oct 7 18:25:20 UTC 2011 i686 i686 i386 GNU/Linux root@office:/home/markus# brctl addbr test root@office:/home/markus# ip -6 addr add 2001:DB8:4309:2388::2/64 dev test root@office:/home/markus# ifconfig test up root@office:/home/markus# ifconfig test test Link encap:Ethernet HWaddr fa:12:c8:34:79:69 inet6 addr: 2001:db8:4309:2388::2/64 Scope:Global UP BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) root@office:/home/markus# ping6 2001:DB8:4309:2388::2 PING 2001:DB8:4309:2388::2(2001:db8:4309:2388::2) 56 data bytes ^C --- 2001:DB8:4309:2388::2 ping statistics --- 7 packets transmitted, 0 received, 100% packet loss, time 5999ms root@office:/home/markus# The address is correctly assigned to the interface, but it can't be pinged. This used to work in natty: root@yavin:/home/markus# uname -a Linux yavin 2.6.38-12-virtual #51-Ubuntu SMP Wed Sep 28 17:57:49 UTC 2011 i686 i686 i386 GNU/Linux root@yavin:/home/markus# brctl addbr test root@yavin:/home/markus# ip -6 addr add 2001:DB8:4309:2388::2/64 dev test root@yavin:/home/markus# ifconfig test up root@yavin:/home/markus# ifconfig test test Link encap:Ethernet HWaddr 0a:38:75:60:be:f1 inet6 addr: fe80::838:75ff:fe60:bef1/64 Scope:Link inet6 addr: 2001:db8:4309:2388::2/64 Scope:Global UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:17 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:0 (0.0 B) TX bytes:1446 (1.4 KB) root@yavin:/home/markus# ping6 2001:DB8:4309:2388::2 PING 2001:DB8:4309:2388::2(2001:db8:4309:2388::2) 56 data bytes 64 bytes from 2001:db8:4309:2388::2: icmp_seq=1 ttl=64 time=0.035 ms 64 bytes from 2001:db8:4309:2388::2: icmp_seq=2 ttl=64 time=0.034 ms 64 bytes from 2001:db8:4309:2388::2: icmp_seq=3 ttl=64 time=0.034 ms ^C --- 2001:DB8:4309:2388::2 ping statistics --- 3 packets transmitted, 3 received, 0% packet loss, time 1999ms rtt min/avg/max/mdev = 0.034/0.034/0.035/0.004 ms root@yavin:/home/markus# To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/894272/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp