HeartBeating Over IP Alias

Overview:

In general, HACMP subnetting requirements can be complicated to understand and may require that you reconfigure networks in AIX® to avoid features such as multiple subnet routes, which can lead to a single point of failure for network traffic.

When planning your cluster networks, you may need to:
Reconfigure IP addresses of HACMP interfaces that will be used at boot time
or
Update/etc/hosts with the new boot time IP addresses.

Heartbeating over IP Aliases is useful because it:
Uses automatically generated IP aliases for heartbeating

Heartbeating over IP Aliasing provides an option where the addresses used for heartbeating can be automatically configured by HACMP in a subnet range that is outside of the range used for the base NIC or any service addresses.

Although Heartbeating over IP Aliasing automatically configures proper aliases for heartbeating, you must still be aware of the implications of subnet routing for all boot and service IP addresses. That is, failure to plan subnets properly can lead to application failures that are not detectable by HACMP. Reliable HACMP cluster communication still requires that the interfaces on a single network can communicate with the other nodes on that network. 

Enables you to avoid reconfiguration of boot time addresses and /etc/hosts.

RSCT sets up the heartbeat rings to go over a separate range of IP aliases. This lets you use a specified subnet in a non-routable range for a heartbeat ring, preserving your other subnets for routable traffic. This also allows you to avoid reconfiguring boot time addresses and entries in /etc/hosts.
Makes HACMP topology configuration easier to understand.
Does not require that you obtain additional routable subnets from the network administrator.

For instance, you can use heartbeating over aliases in HACMP, if due to the network system administration restrictions, the IP addresses that your system can use at boot time must reside on the same subnet. (In general, if there are no system administration restrictions, the IP addresses that your system can use at boot time can reside on either the same or different subnets).