Dell N3200-ON EMC Networking N-Series Switches User Guide version 6.6.3 - Page 260

The NSF checkpoint service allows the stack master 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. NOTE: The switch cannot guarantee that a standby unit has exactly the same data that the stack master has when it fails. For example, the stack master might fail before the checkpoint service gets data to the standby if an event occurs shortly before a failover. Table 8-1 lists the applications on the switch that checkpoint data and describes the type of data that is checkpointed. Table 8-1. Applications that Checkpoint Data Application ARP Auto VOIP Captive Portal DHCP server DHCP snooping DOT1Q DOT1S 802.1X DOT3ad IGMP/MLD Snooping IPv6 NDP iSCSI LLDP OSPFv2 OSPFv3 Route Table Manager Checkpointed Data Dynamic ARP entries Calls in progress Authenticated clients Address bindings (persistent) DHCP bindings database Internal VLAN assignments Spanning tree port roles, port states, root bridge, etc. Authenticated clients Port states Multicast groups, list of router ports, last query data for each VLAN Neighbor cache entries Connections List of interfaces with MED devices attached Neighbors and designated routers Neighbors and designated routers IPv4 and IPv6 dynamic routes 260 Stacking