The IPv6 networking stack has a new feature, Duplicate Address Detection
(DAD), that was not previously available in IPv4. When an address
is being added, the DAD detects a duplicate address that is already
being used on the network. It sends out a multicast message to the
network neighborhood, and requires at least one second to listen
for responses from other nodes. If no responses are received in
that time, the relocatable IPv6 address is considered free to use. For
more information regarding this feature, please refer to the RFC
2462.
The effect of this feature on Serviceguard is that the time
required to add each IPv6 relocatable address will be at least one
second longer than adding a corresponding IPv4 address. Depending
on the number of IPv6 addresses configured within a package, this
could have a moderate to significant impact on package start time.
If you do not need duplicate address detection, you can disable
the DAD feature by setting the kernel parameter ip6_nd_dad_solicity_count
to 0. Please note that this kernel parameter applies to the entire
system. If you turn it off, you disable it for all applications
on the system. For systems where DAD is not required, disabling
this feature can significantly improve the start time of package
packages containing a large number of IPv6 relocatable addresses.
To determine the current state of DAD on your system, use
the ndd -get command to see the current value of the kernel parameter.
# ndd -get /dev/ip6 ip6_nd_dad_solicit_count
If the result is 1, the feature is turned on. If the result
is 0, the feature is turned off.To temporarily change the state
of DAD on your computer, use the ndd -set command to change the
kernel parameter.
# ndd -set /dev/ip6 ip6_nd_dad_solicit_count n
where n is a number: either 1 to turn the feature on, or
0 to turn it off.
To change the state of DAD on your computer so that it will
remain changed even after a reboot, add the following entries to
the /etc/rc/config.d/nddconf file:
# TRANSPORT_NAME[index]=ip6
# NDD_NAME[index]=ip6_nd_dad_solicit_count
# NDD_VALUE[index]=n
Where index is the next available integer value of the nddconf file, and n is a number: either 1 to turn the feature ON or 0
to turn it OFF.
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