TCP/IP (Parallel Library) Configuration and Management Manual

Introduction
HP NonStop TCP/IP (Parallel Library) Configuration and Management Manual—522271-006
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Ethernet Failover
Ethernet Failover
Ethernet failover, available with the G06.10 RVU of Parallel Library TCP/IP, provides
fault tolerance at the adapter level. With Ethernet failover, you can configure your
network to continue running if an adapter fails or during maintenance and replacement
of an adapter.
Ethernet failover allows TCP and UDP sessions to continue operating if there are
cabling or adapter failures. With Ethernet failover, network traffic automatically
migrates from the faulty LIF to the working LIF.
Gains in Scalability
Unlike other failover implementations, Parallel Library TCP/IP Ethernet failover does
not require one of the LIFs to act as a “hot standby” in anticipation of a failure. Both
LIFs are active, allowing inbound and outbound network traffic to be distributed
between them. Therefore, you gain scalability when all your adapters are functioning
correctly.
In Parallel Library TCP/IP, a total of 64 SUBNETs can be configured. To achieve a
failover configuration, two SUBNETs are associated as a failover pair, so a maximum
of 32 failover pairs can be configured.
Shared and Non-Shared IP Addresses
With Ethernet failover, a single IP address can be shared between both LIFs (referred
to as shared IP), or each LIF can be configured to have its own IP address (referred to
as non-shared IP). HP recommends the shared IP configuration for most cases
because shared IP provides a bandwidth advantage for outbound traffic. With shared
IP, outbound traffic can flow over either SUBNET, and this effectively doubles the
throughput capacity for outbound traffic. New connections are distributed across both
adapters, but won't necessarily be distributed in a balanced manner. The benefits of
shared IP are increased bandwidth for outbound traffic and flexibility for inbound traffic.
Non-shared IP can provide the extra bandwidth for outbound traffic that shared IP
provides if you add two routes to each subnet and if the application has selected
INADDR_ANY as a source IP address (allowing Parallel Library TCP/IP to choose the
interface to assign to it). If the application binds to a source IP address, Parallel Library
TCP/IP assigns the outbound traffic to the subnet assigned to that IP address.
Non-shared IP allows you to control the inbound traffic load, forcing the connections to
be distributed over the two interfaces presented by the different IP addresses. This is
handy when you have limited hardware resources or you want to maximize the use of
LIFs. Both LIFs of a failover pair must be cabled to the same network segment. If
different IP addresses are used, the IP addresses must be on the same network
subnet.
When a shared IP failover pair is configured, Parallel Library TCP/IP distributes new
sessions over the two LIFs of the pair. In a similar fashion, each session is assigned
one of the LIFs from the pair for its outbound traffic.