Managing Serviceguard Eighteenth Edition, September 2010

Recommendations for IPv6-Only Mode
IMPORTANT: Check the current Serviceguard release notes for the latest instructions
and recommendations.
• If you decide to migrate the cluster to IPv6-only mode, you should plan to do so
while the cluster is down.
What Is Mixed Mode?
If you configure mixed mode (HOSTNAME_ADDRESS_FAMILY set to ANY), then the
addresses used by the cluster, including the heartbeat, and Quorum Server addresses
if any, can be IPv4 or IPv6 addresses. Serviceguard will first try to resolve a node's
hostname to an IPv4 address, then, if that fails, will try IPv6.
Rules and Restrictions for Mixed Mode
IMPORTANT: See the latest version of the Serviceguard release notes for the most
current information on these and other restrictions.
• The hostname resolution file on each node (for example, /etc/hosts) must
contain entries for all the IPv4 and IPv6 addresses used throughout the cluster,
including all STATIONARY_IP and HEARTBEAT_IP addresses as well any private
addresses. There must be at least one IPv4 address in this file (in the case of
/etc/hosts, the IPv4 loopback address cannot be removed).
In addition, the file must contain the following entry:
::1 localhost ipv6-localhost ipv6-loopback
For more information and recommendations about hostname resolution, see
“Configuring Name Resolution” (page 218).
• You must use $SGCONF/cmclnodelist, not ~/.rhosts or /etc/hosts.equiv,
to provide root access to an unconfigured node.
See “Allowing Root Access to an Unconfigured Node” (page 216) for more
information.
• Hostname aliases are not supported for IPv6 addresses, because of operating
system limitations.
NOTE: This applies to all IPv6 addresses, whether
HOSTNAME_ADDRESS_FAMILY is set to IPV6 or ANY.
• Cross-subnet configurations are not supported.
This also applies if HOSTNAME_ADDRESS_FAMILY is set to IPV6. See
“Cross-Subnet Configurations” (page 41) for more information.
142 Planning and Documenting an HA Cluster