Managing Serviceguard Eighteenth Edition, September 2010

cmhaltnode command is issued or on all nodes in the cluster if a cmhaltcl
command is issued.
• Configurable behavior: NETWORK_AUTO_FAILBACK = NO. Serviceguard will detect
and log the recovery of the interface, but will not switch the IP address back from
the standby to the primary interface.
You can tell Serviceguard to switch the IP address back to the primary interface
by means of the cmmodnet command:
cmmodnet -e <interface>
where <interface> is the primary interface.
The purpose of the NETWORK_AUTO_FAILBACK parameter is to allow you control
Serviceguard's behavior if you find network interfaces are experiencing a “ping-pong”
effect, switching back and forth unduly between primary and standby interfaces. If
you are not seeing any such problem, leave NETWORK_AUTO_FAILBACK set to YES.
You can track switching behavior in the syslog file.
NOTE: The NETWORK_AUTO_FAILBACK setting applies only to link-level failures,
not to failures at the IP level; see “Monitoring LAN Interfaces and Detecting Failure:
IP Level” (page 98) for more information about such failures. For more information
about the cluster configuration file, see “Cluster Configuration Parameters ” (page 143).
Remote Switching
A remote switch (that is, a package switch) involves moving packages to a new system.
In the most common configuration, in which all nodes are on the same subnet(s), the
package IP (relocatable IP; see “Stationary and Relocatable IP Addresses ” (page 90))
moves as well, and the new system must already have the subnet configured and
working properly, otherwise the packages will not be started.
NOTE: It is possible to configure a cluster that spans subnets joined by a router, with
some nodes using one subnet and some another. This is called a cross-subnet
configuration. In this context, you can configure packages to fail over from a node on
one subnet to a node on another, and you will need to configure a relocatable address
for each subnet the package is configured to start on; see “About Cross-Subnet Failover”
(page 201), and in particular the subsection “Implications for Application Deployment”
(page 202).
When a remote switch occurs, TCP connections are lost. TCP applications must reconnect
to regain connectivity; this is not handled automatically. Note that if the package is
dependent on multiple subnets (specified as monitored_subnets in the package
configuration file), all those subnets must normally be available on the target node
before the package will be started. (In a cross-subnet configuration, all subnets
How the Network Manager Works 97