Managing Serviceguard 13th Edition, February 2007

Understanding Serviceguard Software Components
How the Network Manager Works
Chapter 3 109
Figure 3-18 Local Switching After Cable Failure
Local network switching will work with a cluster containing one or more
nodes. You may wish to design a single-node cluster in order to take
advantage of this local network switching feature in situations where
you need only one node and do not wish to set up a more complex cluster.
Switching Back to Primary LAN Interfaces after Local Switching
If a primary fails, the subnet will be switched to a standby. If the primary
is later restored, the cluster daemon will switch the subnets back to their
primary interfaces. Whenever a node is halted, the cluster daemon
(cmcld) will always attempt to switch any Serviceguard-configured
subnets running on standby interfaces back to their primary interfaces.
This is done regardless of the link state of the primary interfaces. The
intent of this switchback is to preserve the original network
configuration as it was before the cluster started. Switching back occurs
on the specified node if a cmhaltnode command is issued or on all nodes
in the cluster if a cmhaltcl command is issued.