Managing Serviceguard 14th Edition, June 2007

Understanding Serviceguard Software Components
How the Network Manager Works
Chapter 398
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, switching
them when necessary.
Stationary and Relocatable IP Addresses
Each node (host system) should have at least one IP address for each
active network interface. This address, known as a stationary IP
address, is configured in the node's /etc/rc.config.d/netconf file or
in the node’s /etc/rc.config.d/netconf-ipv6 file. A stationary IP
address is not transferable to another node, but may be transferable to a
standby LAN interface card. The stationary IP address is not associated
with packages. Stationary IP addresses are used to transmit heartbeat
messages (described earlier in the section “How the Cluster Manager
Works”) and other data.
In addition to the stationary IP address, you normally assign one or more
unique IP addresses to each failover package. The package IP address is
assigned to the primary LAN interface card by the cmmodnet command
in the package control script when the package starts up.
The IP addresses associated with a package are called relocatable IP
addresses (also known as 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 150 packages. This can be a combination
of IPv4 and IPv6 addresses.
Because system multi-node and multi-node packages do not failover, they
do not have relocatable IP address.
A relocatable IP address is like a virtual host IP address that is assigned
to a package. It is recommended that you configure names for each
package through DNS (Domain Name Service). A program then can use
the package's name like a host name as the input to gethostbyname(),
which will return the package's relocatable IP address.