Managing Serviceguard Nineteenth Edition, Reprinted June 2011

Redundant Network Components
To eliminate single points of failure for networking, each subnet accessed by a cluster node is
required to have redundant network interfaces. Redundant cables are also needed to protect
against cable failures. Each interface card is connected to a different cable, and the cables
themselves are connected by a component such as a hub or a bridge. This arrangement of physical
cables connected to each other via a bridge or concentrator or switch is known as a bridged net
.
IP addresses can be associated with interfaces on a bridged net. An interface that has an IP address
associated with it is known as a primary interface, and an interface that does not have an IP
address associated with it is known as a standby interface. Standby interfaces are those which
are available for switching by Serviceguard if a failure occurs on the primary. When Serviceguard
detects a primary interface failure, it will switch the IP addresses and any associated connections
from the failed interface card to a healthy standby interface card. In addition, if a LAN card fails
on startup, or cannot be detected because of other hardware failures, Serviceguard will effect a
switch to a standby if there is one available in the same bridged net.
Serviceguard supports a maximum of 30 network interfaces per node. For this purpose an interface
is defined as anything represented as a LAN interface in the output of lanscan (1m), so the
total of 30 can comprise any combination of physical LAN ports, VLAN ports, IPoIB interfaces and
APA aggregates. (A node can have more than 30 such interfaces, but only 30 can be part of the
cluster configuration.)
A selection of network configurations is described further in the following sections. See also “How
the Network Manager Works ” (page 64). For detailed information about supported network
configurations, consult Hewlett-Packard support.
NOTE: Serial (RS232) lines are no longer supported for the cluster heartbeat.
Fibre Channel, Token Ring and FDDI networks are no longer supported as heartbeat or data LANs.
Rules and Restrictions
• A single subnet cannot be configured on different network interfaces (NICs) on the same node.
• In the case of subnets that can be used for communication between cluster nodes, the same
network interface must not be used to route more than one subnet configured on the same
node.
• For IPv4 subnets, Serviceguard does not support different subnets on the same LAN interface.
◦ For IPv6, Serviceguard supports up to two subnets per LAN interface (site-local and global).
• Serviceguard does support different subnets on the same bridged network (this applies at both
the node and the cluster level).
• Serviceguard does not support using networking tools such as ifconfig or the configuration
file /etc/rc.config.d/netconf to add IP addresses to network interfaces that are
Redundant Network Components 27