# IPv6 DAD disables IPv6 Traffic, how to turn IPv6 back on?



## benzh512 (Mar 6, 2009)

Running FreeBSD 7.1, testing Duplicate Address Detection, when I intentionally set duplicate Link Local Address, dmesg shows:

em1: DAD detected duplicate IPv6 address fe80:4::217:a4ff: fe51: fb0d: NS in/out=0/3, NA in=1
em1: DAD complete for fe80:4::217:a4ff: fe51: fb0d - duplicate found
em1: manual intervention required
em1: possible hardware address duplication detected, disable IPv6

After that all IPv6 traffic seem to be off, ifconfig down/up didn't work.

Any idea how to turn IPv6 back on? Thanks!


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## DutchDaemon (Mar 6, 2009)

Long shot:

/etc/rc.d/netif restart && sleep 30  && /etc/rc.d/routing restart


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## benzh512 (Mar 7, 2009)

Thanks for the reply, unfortunately, it didn't work.

After doing the restart, I turned on debug, and saw the following in /var/log/messages

Mar  7 00:22:26 gtw64 kernel: em1: got interface identifier from itself
Mar  7 00:22:26 gtw64 kernel: em1: ifid: 02:17:a4: ff: fe: 51: fb:0d
Mar  7 00:22:26 gtw64 kernel: em1: link state changed to DOWN
Mar  7 00:22:26 gtw64 kernel: em1: starting DAD for fe80:4::217:a4ff: fe51: fb0d
Mar  7 00:22:27 gtw64 kernel: em1: starting DAD for fe80:4::217:a4ff: fe51: f989
Mar  7 00:22:28 gtw64 kernel: em1: link state changed to UP
Mar  7 00:22:30 gtw64 kernel: em1: DAD complete for fe80:4::217:a4ff: fe51: f989 - no duplicates found
Mar  7 00:22:30 gtw64 kernel: em1: DAD complete for fe80:4::217:a4ff: fe51: fb0d - no duplicates found

The reason I say it's not working was because, although it says em1 is doing DAD for the Link Local Addrs, but I see no Neighbor Solicitation messages coming out of the interface, and no more IPv6 traffic is being processed...

Any suggestions?

Thanks!


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## DutchDaemon (Mar 7, 2009)

Well, there's always a reboot, I guess. If you set the duplicate address by hand it should vanish after a reboot, right?


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## benzh512 (Mar 7, 2009)

ya...but the problem is, I am doing the TAHI testing, and there is still the second half of the test case to run... it requires the box to be connected to the "controller" (by running some agent in the background), reboot will shut down the connection so the test won't run...


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## DutchDaemon (Mar 7, 2009)

Maybe go one step further than up/down and restarting the network: try the ifconfig destroy and ifconfig create commands (man ifconfig). Maybe the card needs to be re-initialised to take on IPv6 again.


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## benzh512 (Mar 10, 2009)

well, I am not quite sure how does the "ifconfig create" interface work, and I think the test requires a physical interface.

I figured out a way to run the test without the script so I can reboot the box between the first and the second half of the test case.

Still, thanks for all your help!


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