Managing Serviceguard 13th Edition, February 2007

Understanding Serviceguard Hardware Configurations
Redundant Network Components
Chapter 2 39
Figure 2-1 Redundant LANs
In the figure, a two-node Serviceguard cluster has one bridged net
configured with both a primary and a standby LAN card for the
data/heartbeat subnet (Subnet A). Another LAN card provides an
optional dedicated heartbeat LAN. Note that the primary and standby
LAN segments are connected by a hub to provide a redundant
data/heartbeat subnet. Each node has its own IP address for this subnet.
In case of a failure of a primary LAN card for the data/heartbeat subnet,
Serviceguard will perform a local switch to the standby LAN card on the
same node.
Redundant heartbeat is provided by the primary LAN and the dedicated
LAN which are both carrying the heartbeat. In Figure 2-1, local
switching is not needed for the dedicated heartbeat LAN, since there is
already a redundant path via the other subnet. In case of data congestion
on the primary LAN, the dedicated heartbeat LAN will prevent a false
diagnosis of heartbeat failure. Each node has its own IP address for the
dedicated heartbeat LAN.