Users Guide

Automatic and Manual Stack Unit Failover
Stack unit failover is the process of the standby unit becoming a management unit.
Dell Networking OS fails over to the standby stack unit when:
1. Communication is lost between the standby and primary stack unit.
2. You request a failover via the CLI.
To display the reason for the last failover, use the show redundancy command from EXEC Privilege mode.
Example of the show redundancy Command
Dell#show redundancy
-- Stack-unit Status --
------------------------------------------------
Mgmt ID: 0
Stack-unit ID: 0
Stack-unit Redundancy Role: Primary
Stack-unit State: Active
Stack-unit SW Version: 9.6(0.0)
Link to Peer: Down
Peer Stack-unit: not present
-- Stack-unit Redundancy Configuration --
------------------------------------------------
Primary Stack-unit: mgmt-id 0
Auto Data Sync: Full
Failover Type: Hot Failover
Auto reboot Stack-unit: Enabled
Auto failover limit: 3 times in 60 minutes
-- Stack-unit Failover Record --
------------------------------------------------
Failover Count: 0
Last failover timestamp: None
Last failover Reason: None
Last failover type: None
-- Last Data Block Sync Record: --
------------------------------------------------
Stack Unit Config: no block sync done
Start-up Config: no block sync done
Runtime Event Log: no block sync done
Running Config: no block sync done
ACL Mgr: no block sync done
LACP: no block sync done
STP: no block sync done
SPAN: no block sync done
Dell#
Support for RPM Redundancy by Dell Networking OS Version
Dell Networking OS supports increasing levels of RPM redundancy (warm and hot) as described in the table below.
Table 31. Support for RPM Redundancy by Dell Networking OS Version
Platform Failover Type Failover Behavior
S4820T Hot Failover Only the failed RPM reboots. All the line
cards and SFMs remain online. All
application tasks are spawned on the
secondary RPM before failover. The
High Availability (HA)
337