Managing HP Serviceguard A.12.00.00 for Linux, June 2014

3.5.1 Stationary and Relocatable IP Addresses and Monitored Subnets
Each node (host system) should have an IP address for each active network interface. This address,
known as a stationary IP address, is configured in the file
/etc/sysconfig/network-scripts/ifcfg-<interface> on Red Hat or
/etc/sysconfig/network/ifcfg-<mac_address> on SUSE. The stationary IP address is
not associated with packages, and it is not transferable to another node.
Stationary IP addresses are used to transmit data, heartbeat messages (described under “How the
Cluster Manager Works ” (page 36)), or both. They are configured into the cluster via the cluster
configuration file; see the entries for HEARTBEAT_IP and STATIONARY_IP under “Cluster
Configuration Parameters” (page 89).
Serviceguard monitors the subnets represented by these IP addresses. They are referred to as
monitored subnets, and you can see their status at any time in the output of the cmviewcl
command; see “Network Status” (page 214) for an example.
You can also configure these subnets to be monitored for packages, using the monitored_subnet
parameter in the package configuration file (page 191). A package will not start on a node unless
the subnet(s) identified by monitored_subnet in its package configuration file are up and
reachable from that node.
IMPORTANT: Any subnet identified as a monitored_subnet in the package configuration file
must be configured into the cluster via NETWORK_INTERFACE and either STATIONARY_IP or
HEARTBEAT_IP in the cluster configuration file. See “Cluster Configuration Parameters” (page 89)
and “Package Parameter Explanations” (page 184).
In addition to the stationary IP address, you normally assign one or more unique IP addresses to
each package. The package IP address is assigned to a LAN interface when the package starts
up.
The IP addresses associated with a package are called relocatable IP addresses (also known as
IP aliases, package IP addresses or floating IP addresses) because the addresses can actually move
from one cluster node to another. You can use up to 200 relocatable IP addresses in a cluster
spread over as many as 300 packages. These addresses can be IPv4, IPv6, or a combination of
both address families.
Because system multi-node and multi-node packages do not fail over, they do not have relocatable
IP address.
A relocatable IP address is like a virtual host IP address that is assigned to a package. HP
recommends that you configure names for each package through DNS (Domain Name System).
A program then can use the package’s name like a host name as the input to gethostbyname(3),
which will return the package’s relocatable IP address.
Relocatable addresses (but not stationary addresses) can be taken over by an adoptive node if
control of the package is transferred. This means that applications can access the package via its
relocatable address without knowing which node the package currently resides on.
IMPORTANT: Any subnet that is used by a package for relocatable addresses should be
configured into the cluster via NETWORK_INTERFACE and either STATIONARY_IP or
HEARTBEAT_IP in the cluster configuration file. For more information about those parameters,
see “Cluster Configuration Parameters” (page 89). For more information about configuring
relocatable addresses, see the descriptions of the package ip_ parameters (page 192).
60 Understanding Serviceguard Software Components