Managing HP Serviceguard for Linux, Eighth Edition, March 2008

Understanding Serviceguard Software Components
How the Network Manager Works
Chapter 374
How the Network Manager Works
The purpose of the network manager is to detect and recover from
network card 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, switching them
when necessary.
NOTE Serviceguard monitors the health of the network interfaces (NICs) but
does not perform network connectivity checking.
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 43),
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 110.
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 246 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 217). 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.