Managing HP Serviceguard for Linux, Tenth Edition, September 2012

If there is more than one heartbeat subnet, and there is a failure on one of them,
heartbeats will go through another, so you can configure a smaller MEMBER_TIMEOUT
value.
NOTE: For heartbeat configuration requirements, see the discussion of the
HEARTBEAT_IP parameter later in this chapter. For more information about managing
the speed of cluster re-formation, see the discussion of the MEMBER_TIMEOUT parameter,
and further discussion under “What Happens when a Node Times Out” (page 87), and,
for troubleshooting, “Cluster Re-formations Caused by MEMBER_TIMEOUT Being Set too
Low” (page 300).
About Hostname Address Families: IPv4-Only, IPv6-Only, and Mixed Mode
As of A.11.19, Serviceguard supports three possibilities for resolving the nodes' hostnames
(and Quorum Server hostnames, if any) to network address families:
• IPv4-only
• IPv6-only
• Mixed
IPv4-only means that Serviceguard will try to resolve the hostnames to IPv4 addresses
only.
IMPORTANT: You can configure an IPv6 heartbeat, or stationary or relocatable IP
address, in any mode: IPv4-only, IPv6-only, or mixed. You can configure an IPv4
heartbeat, or stationary or relocatable IP address, in IPv4-only or mixed mode.
IPv6-only means that Serviceguard will try to resolve the hostnames to IPv6 addresses
only.
Mixed means that when resolving the hostnames, Serviceguard will try both IPv4 and
IPv6 address families.
You specify the address family the cluster will use in the cluster configuration file (by
setting HOSTNAME_ADDRESS_FAMILY to IPV4, IPV6, or ANY), or by means of the -a
of cmquerycl (1m); see “Specifying the Address Family for the Cluster Hostnames”
(page 180). The default is IPV4. See the subsections that follow for more information and
important rules and restrictions.
What Is IPv4–only Mode?
IPv4 is the default mode: unless you specify IPV6 or ANY (either in the cluster configuration
file or via cmquerycl -a) Serviceguard will always try to resolve the nodes' hostnames
(and the Quorum Server's, if any) to IPv4 addresses, and will not try to resolve them to
IPv6 addresses. This means that you must ensure that each hostname can be resolved to
at least one IPv4 address.
100 Planning and Documenting an HA Cluster