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. In the case of FDDI networks, each interface
card is connected via a cable to a different concentrator. 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.
A selection of network configurations is described further
in the following sections. For detailed information about supported
network configurations, consult Hewlett-Packard support.
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 | NOTE: Fibre Channel networks are no longer supported
as heartbeat or data LANs. |
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Providing
Redundant FDDI Connections |
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FDDI is a high speed fiber optic interconnect medium. If you
are using FDDI, you can create a redundant configuration by using
a star topology to connect all the nodes to two concentrators, which
are also connected to two routers, which communicate with the world
outside the cluster. In this case, you use two FDDI cards in each
node. The configuration is shown in Figure 2-2 “Redundant
FDDI Configuration ”. Note that the concentrators are connected together using
dual cables cross-connected Port A to Port B. The routers must be configured
to send all packets to both concentrators.
Using
Dual Attach FDDI Stations |
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Another way of obtaining redundant FDDI connections is to
configure dual attach stations on each node to create an FDDI ring,
shown in Figure 2-3 “Configuration
with Dual Attach FDDI Stations ”. An advantage
of this configuration is that only one slot is used in the system
card cage. In Figure 2-3 “Configuration
with Dual Attach FDDI Stations ”, note that
nodes 3 and 4 also use Ethernet to provide connectivity outside
the cluster.
The use of dual attach cards gives protection against failures
in both cables and connectors, but does not protect against card
failures. LAN card failure would result in a package switching to
another node.
Replacement
of Failed Network Cards |
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Depending on the system configuration, it is possible to replace
failed network cards while the cluster is running. The process is
described under “Replacement of LAN Cards” in
the chapter “Troubleshooting Your Cluster.”
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