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Date: Sun, 30 Jun 2013 19:48:52 -0400
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Subject: Duplicate Address Detection misfire?
From: Zaphod Beeblebrox <zbeeble@gmail.com>
To: FreeBSD Net <freebsd-net@freebsd.org>
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I have a FreeBSD 9.1-RELEASE vmware guest running. It is using the
"bridged" type of networking with VMWare.  It gets it's IPv4 address from
DHCP (successfully) and then fails to initialize IPv6.  The relevant
rc.conf is:

ipv6_activate_all_interfaces="YES"
ifconfig_em0_ipv6="inet6 accept_rtadv"
ip6addrctl_verbose="YES"

The console output says:

em0: DAD detected duplicate IPv6 address fe80:2::20c:29ff:fe0a:3989: NS
in/out=2/1, NA in=0
em0: DAD complete for fe80:2::20c:29ff:fe0a:3989 - duplicate found
em0: manual intervention required
em0: possible hardware address duplication deteted, disable IPv6

And subsequently, em0's nd6 has "IFDISABLED" in it.

With wireshark, I see two ICMPv6 neighbor solicitations that are identical
--- is this the problem?

How do I fix this?