Managing Serviceguard Nineteenth Edition, Reprinted June 2011

monitored_subnet_access unconfigured for a monitored subnet is equivalent to
FULL.)
(For legacy packages, see “Configuring Cross-Subnet Failover” (page 295).)
• You should not use the wildcard (*) for node_name (page 223) in the package configuration
file, as this could allow the package to fail over across subnets when a node on the same
subnet is eligible. Failing over across subnets can take longer than failing over on the same
subnet. List the nodes in order of preference instead of using the wildcard.
• Each subnet interface (NIC) used by the package must have a standby interface on the local
bridged net.
The standby interface can be shared between subnets.
• Deploying applications in this environment requires careful consideration; see “Implications
for Application Deployment” (page 146).
• If a monitored_subnet (page 229) is configured for PARTIAL
monitored_subnet_access in a package’s configuration file, it must be configured on
at least one of the nodes on the node_name list for that package.
Conversely, if all of the subnets that are being monitored for this package are configured for
PARTIAL access, each node on the node_name list must have at least one of these subnets
configured.
◦ As in other cluster configurations, a package will not start on a node unless the subnets
configured on that node, and specified in the package configuration file as monitored
subnets, are up.
Implications for Application Deployment
Because the relocatable IP address will change when a package fails over to a node on another
subnet, you need to make sure of the following:
• The hostname used by the package is correctly remapped to the new relocatable IP address.
• The application that the package runs must be configured so that the clients can reconnect to
the package’s new relocatable IP address.
In the worst case (when the server where the application was running is down), the client may
continue to retry the old IP address until TCP’s tcp_timeout is reached (typically about ten
minutes), at which point it will detect the failure and reset the connection.
For more information, see the white paper Technical Considerations for Creating a Serviceguard
Cluster that Spans Multiple IP Subnets, at http://www.hp.com/go/hpux-serviceguard-docs.
Configuring a Package to Fail Over across Subnets: Example
To configure a package to fail over across subnets, you need to make some additional edits to the
package configuration file.
NOTE: This section provides an example for a modular package; for legacy packages, see
“Configuring Cross-Subnet Failover” (page 295).
Suppose that you want to configure a package, pkg1, so that it can fail over among all the nodes
in a cluster comprising NodeA, NodeB, NodeC, and NodeD.
NodeA and NodeB use subnet 15.244.65.0, which is not used by NodeC and NodeD; and
NodeC and NodeD use subnet 15.244.56.0, which is not used by NodeA and NodeB. (See
“Obtaining Cross-Subnet Information” (page 181) for sample cmquerycl output).
146 Planning and Documenting an HA Cluster