Migrating X.25 over PSI to XOL

12
High Availability with XOL
The high availability (HA) feature is available in the XOL interface. The x25ifstate command
integrates the XOL interface with the ServiceGuard (SG) scripts to create the SG package in an SG
cluster environment. The SG package protects mission critical applications from hardware and
software failures through the HA feature. In an HA environment, the standby resources automatically
take over if the primary resource fails.
To use the XOL HA feature, the user must provide a user-defined unique MAC address for the LAN
interface. When the XOL interface fails over to the standby LAN interface, this unique MAC address is
used to configure the standby LAN interface.
XOL supports the HA feature for the following failovers:
Local failover
A primary LAN card and a standby LAN card are used to make the XOL interface highly available on
a system. The XOL interface migrates from the primary LAN card to the standby LAN card when the
primary card fails. This HA feature can be configured by editing the values of the parameters,
standby_device and XOL_floating_macaddr, in the XOL configuration file. The ServiceGuard
product is not required for this feature to be available on the local system.
Remote failover
When XOL is integrated with the ServiceGuard package, the XOL interface becomes highly available
in a cluster of nodes. The XOL interface migrates along with the ServiceGuard package to the standby
node if the LAN card on the primary node fails. This feature requires that the ServiceGuard product is
available and configured on all the nodes in the cluster.
Remote Failover with Local Failover
When the primary LAN card on the primary node fails, the HA feature attempts to activate the XOL
interface on the standby LAN card on the primary node. If the XOL interface is not activated on either
the primary or the standby LAN card on the primary node, the ServiceGuard package activates the
XOL interface on the LAN card on the standby node in the SG cluster. This feature requires that the
ServiceGuard product is available and configured on all the nodes in the cluster.
Important:
The failover is not transparent and results in loss of existing XOL
connections and loss of data. After failover, the XOL connections must be
re-established.
For more information on the HA feature available with XOL, see X.25 User Guide at:
http://docs.hp.com/en/netcom.html#X.25
Conclusion
The migration from X.25 over native PSI cards to XOL offers the following benefits:
 Eliminates legacy X.25 infrastructure on the HP-UX host side
 Reduces maintenance and operational costs
 Enables seamless migration of legacy X.25 applications to XOL
 Provides higher throughput with the use of LAN cards
 Enables the use of the same set of commands for XOL and X.25 over PSI