Managing Serviceguard 14th Edition, June 2007

Understanding Serviceguard Software Components
How the Network Manager Works
Chapter 3 105
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 interface fails, the subnet will be switched to a standby. If
the primary interface 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.