Managing Serviceguard Eighteenth Edition, September 2010

NOTE: Even though link-local IP addresses are not supported in the Serviceguard
cluster configuration, the primary link-local address on the Serviceguard primary
interface will be switched over the standby during a local switch. This is because of
two requirements: First, the dual stack (IPv4/IPv6) kernel requires that the primary IP
address associated with an interface must always be a link-local address. Second,
Serviceguard requires that the site-local and global IPs be switched to the standby
network interface.
IPv6 Relocatable Address and Duplicate Address Detection Feature
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_countn
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/nddconffile:
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.
480 IPv6 Network Support