Selecting None activates a standard high availability configuration and NSM failover
functionality, with the option of enabling stateful High Availability.
Active/Standby mode provides basic high availability with the configuration of two
identical NSMs as a High Availability pair. The Active NSM handles all traffic, while the Standby
NSM shares its configuration settings and can take over at any time to provide continuous network
connectivity if the Active NSM stops working.
By default, Active/Standby mode is stateless, meaning that network connections must be re-established after a failover. To avoid this, stateful synchronization can be licensed and enabled with Active/Standby mode. In this stateful High Availability mode, the dynamic state is continuously synchronized between the Active and Standby NSMs. When the Active NSM encounters a fault condition, stateful failover occurs as the Standby NSM takes over the Active role with no interruptions to the existing network connections.
The operative condition of an NSM. The Active identifier is a logical role that
can be assumed by either a primary or secondary NSM.
The principal NSM. The primary identifier is a manual designation and
is not subject to conditional changes. Under normal operating conditions, the primary
NSM operates in an Active role.
The subordinate NSM. The secondary identifier is a relational
designation and is assumed by an NSM when paired with a primary NSM. Under
normal operating conditions, the secondary NSM operates in a standby mode. Upon
failure of the primary NSM, the secondary NSMassumes the Active role.
High Availability: non-state, NSM failover capability.
The actual process in which the Standby NSM assumes the Active role following a
qualified failure of the Active NSM. Qualification of failure is achieved by various
configurable physical and logical monitoring facilities.
Applies to a post-failover condition in which the primary NSM has failed, and the
secondary NSM has assumed the Active role. Enabling Preempt causes the primary
NSM to seize the Active role from the secondary after the primary NSM has been
restored to a verified operational state.
The passive condition of an NSM. The standby identifier is a logical role that
can be assumed by either a primary or secondary NSM. The Standby
NSM assumes the Active role upon a determinable failure of the Active NSM.