Cluster I/O Protocols (CIP) Configuration and Management Manual (H06.16+, J06.05+)

ROUTE PRIORITY attribute value are considered. If there is more than one with the same highest
value, one is round-robin selected from that group. CLIMs with no ROUTE object are considered
to have the lowest priority, and if those are all that are available, one of them is round-robin
selected.
6. If no available CLIMs have a default network-route entry, then no route can be found. Return
an error to the application.
Failover in the CIP Subsystem
CIP failover allows the resources associated with a failing interface to be switched to another
interface so they remain available to the external network with minimal impact on socket
applications.
Upon failure of one or more Ethernet interfaces or an entire CLIM, CIP can ensure the availability
of the interface resources such as IP addresses, sockets, connections, routes, and tunnels by either
sharing those resources among multiple physical interfaces on the same CLIM or migrating them
to another interface on a different CLIM. While most resources can be migrated during failover,
some are lost if migration to a different CLIM is required. This section defines resources and
describes their treatment in failover situations.
There are two types of failover in CIP: failover from one interface to another in the same CLIM,
and failover from one CLIM to another.
Intra-CLIM Failover – Overview
Intra-CLIM failover occurs when a link to the external network has failed, but the CLIM is still
operational. It is configured and handled completely within the CLIM by using bonded interfaces.
The NonStop operating system does not need to take any action. All interface resources are
switched without disruption.
Bonded interfaces share interface resources among multiple physical interfaces. They can be
configured to be similar to NonStop TCP/IPv6 failover with the SHAREDIP option except that the
interfaces must be in the same CLIM and are not limited to just two interfaces. Bonded interfaces
do not support a mode similar to the NonStop TCP/IPv6 NONSHAREDIP option in which each
interface has a different IP address until failover.
Figure 5: Intra-CLIM Interface Failover (page 37) illustrates intra-CLIM failover. The figure uses
shaded rectangles to show CLIM interfaces, ovals for the resources using those interfaces, and
lines for the physical interfaces associated with them. Bonded interface bond1 is defined in the
CLIM to consist of the two slave physical interfaces: eth1 and eth2. If either slave interface goes
down, the other takes its traffic with no disruption. The NonStop OS tracks the bonded interface,
not the slave interfaces, so no changes are made in the NonStop OS tables or resource locations
when this occurs.
36 Overview