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

same IP address is re-created in the failover CLIM. Any state-changing operations done on
the socket since the bind (such as listen or setsockopt) are repeated in the failover CLIM.
• Socket lost. When a socket has a TCP or SCTP connection, it is also removed on all but one
CLIM if this was not already been done by a previous bind. Sockets associated with TCP and
SCTP connections do not survive a failure. Each such socket is marked to return an error to
the NonStop application on its next or current socket call.
For TCP sockets, the failover CLIM attempts to reset the connection. This reset is not issued for
SCTP sockets.
A UDP connect by itself does not affect failover handling. UDP sockets always fall into the No
migration needed or the Socket migrated categories. For UDP sockets that have joined
a multicast group, the IP multicast addresses are moved to the failover CLIM. During migration of
UDP sockets, a transient loss of data may occur.
IP Addresses
All IP addresses associated with an interface are migrated during failover. Before an address can
be added to the failover CLIM, it must be removed from the home CLIM. When the failover addresses
are all removed from the network, the failover CLIM adds them to the failover interface and tells
the host to update its interface tables.
IPv4 Addresses
Static IPv4 addresses are part of the configuration files copied to the failover CLIM from the home
CLIM and are migrated by adding them to the destination interface.
Duplicate IP address checking is not done for IPv4 addresses. The failover and home interfaces
are tried alternately until one succeeds or the CLIM object is stopped. If it has not completed after
a certain time, the failover operation is declared a failure and all sockets are marked to return an
error on the current or next socket call.
IPv6 Addresses
Static IPv6 addresses are also part of the configuration files copied to the failover CLIM from the
home CLIM and are migrated by adding the failover addresses to the destination interface. The
link-local IPv6 address is derived from the MAC address of the home interface and is migrated by
adding it to the destination interface.
Auto configured IPv6 addresses are derived from the MAC address of the home interface and
prefixes advertised by routers in the external network. Since both interfaces of a failover pair must
be in the same broadcast domain, it is assumed they have the same prefixes. They are added to
the destination interface by using the prefixes in the auto-configured addresses of the home resources
for the destination interface. As the prefixes change or expire, the same changes are made to the
failed over auto-configuration addresses.
IPv6 automatically performs duplicate IP address checking. Duplicate addresses remain assigned
to the interface, but marked as tentative. If an address is still marked tentative after a certain time,
all the addresses are removed and the alternate interface is tried until one succeeds or the CLIM
object is stopped.
Multicast Addresses
IPv4 and IPv6 multicast addresses are added by applications when they join multicast groups by
means of the setsockopt() call. The NonStop host system code saves these addresses along with
their associated interfaces as it passes them to the CLIM. If the interface requires failover, the same
multicast groups are joined on the failover interface. Duplicate-address checking is not needed.
A solicited-node multicast address exists for each unicast address and is failed over with the unicast
address.
46 Overview