Managing HP Serviceguard for Linux, Seventh Edition, July 2007

Understanding Serviceguard Software Components
How the Network Manager Works
Chapter 3 71
How the Network Manager Works
The purpose of the network manager is to detect and recover from
network card and cable failures so that network services remain highly
available to clients. In practice, this means assigning IP addresses for
each package to the primary LAN interface card on the node where the
package is running and monitoring the health of all interfaces.
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 earlier under “How the Cluster Manager Works” on page 39),
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” starting on page 106.
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” on page 234 for an example.
You can also configure these subnets to be monitored for packages, using
the monitored_subnet parameter in the package configuration file (see
page 208). 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.
Any subnet identified as a monitored_subnet in the package
configuration file must be configured (as a STATIONARY_IP or
HEARTBEAT_IP) in the cluster configuration file.