Users Guide

264 Stacking
the case of configuration data, or the management unit in the stack can
checkpoint this data directly to the standby unit active processes, as in the
case of operational data.
Use the show nsf command to view the stack checkpoint status prior to
reloading a stack member. Do not reload while a checkpoint operation is in
progress.
The NSF checkpoint service allows the management unit in the stack to
communicate startup configuration data to the standby unit in the stack.
When the stack selects a standby unit, the checkpoint service notifies
applications to start a complete checkpoint. After the initial checkpoint is
done, applications checkpoint changes to their data every 120 seconds.
Table 8-1 lists the applications on the switch that checkpoint data and
describes the type of data that is checkpointed.
NOTE: The switch cannot guarantee that a standby unit has exactly the same data
that the management unit in the stack has when it fails. For example, the
management unit in the stack might fail before the checkpoint service gets data to
the standby if an event occurs shortly before a failover.
Table 8-1. Applications that Checkpoint Data
Application Checkpointed Data
ARP Dynamic ARP entries
Auto VOIP Calls in progress
Captive Portal Authenticated clients
DHCP server Address bindings (persistent)
DHCP snooping DHCP bindings database
DOT1Q Internal VLAN assignments
DOT1S Spanning tree port roles, port states, root bridge, etc.
802.1X Authenticated clients
DOT3ad Port states
IGMP/MLD Snooping Multicast groups, list of router ports, last query data for
each VLAN
IPv6 NDP Neighbor cache entries