Intel GigE NIC Issue on IPv6 DAD

[Siquijor Philips]

Hi,

I'm currently doing IPv6 conformance testing with FreeBSD-7.1 RELEASE
however I've encountered DAD timing issue on Intel Gigabit NICs with
em(4) driver. I configure several tweaks on net.inet6.ip6.dad_count
such as 2 seconds, 3 seconds and 4 seconds just to get the specific
DAD timing on each test item. There are 29 test items for a router
category on RFC 4862 (IPv6 Stateless Address Autoconfiguration) and
some items passed on 4 seconds, others passed on 1 second (default DAD
configuration) while others are not consistent (sometimes passed on 4
seconds and if tested again, it will satisfy on 1 second). With FastE
NICs such as Intel 10/100 with fxp(4) driver and Via Rhine 10/100 with
vr(4) driver, these cards just works fine using the default
net.inet6.ip6.dad_count=1 (1 second) without this DAD timing problem.

So my concern is, why does Intel GigE NICs with em(4) driver behave
this way? I have tested 2 Intel GigE NICs with different chipsets,
82541and 82574L and it does the same behavior? Is this a bug or
something?

Regards,
Siquijor