Managing Serviceguard Fifteenth Edition, reprinted May 2008

Understanding Serviceguard Software Components
How the Network Manager Works
Chapter 3 101
various combinations) can be defined as stationary IPs in a cluster. Both
IPv4 and IPv6 addresses also can be used as relocatable (package) IP
addresses.
Adding and Deleting Relocatable IP Addresses
When a package is started, a relocatable IP address can be added to a
specified IP subnet. When the package is stopped, the relocatable IP
address is deleted from the specified subnet. These functions are
performed by the cmmodnet command in the package master control
script (package control script for legacy packages).
IP addresses are configured only on each primary network interface
card; standby cards are not configured with an IP address. Multiple IPv4
addresses on the same network card must belong to the same IP subnet.
Load Sharing
It is possible for one package to have multiple services that are
associated with the same IP address. If one service is moved to a new
system, then the other services using the IP address will also be moved.
Load sharing can be achieved by creating a package for each service and
giving the package a unique IP address. This gives the administrator the
ability to move selected services to less loaded systems.
Monitoring LAN Interfaces and Detecting Failure
At regular intervals, Serviceguard polls all the network interface cards
specified in the cluster configuration file. Network failures are detected
within each single node in the following manner. One interface on the
node is assigned to be the poller. The poller will poll the other primary
and standby interfaces in the same bridged net on that node to see
whether they are still healthy. Normally, the poller is a standby
interface; if there are no standby interfaces in a bridged net, the primary
interface is assigned the polling task. (Bridged nets are explained in
“Redundant Network Components” on page 38 in Chapter 2.)
The polling interface sends LAN packets to all other interfaces in the
node that are on the same bridged net and receives packets back from
them.