White Papers

MAC Addressing
All port interfaces in the stack use the MAC address of the management interface on the master switch. The MAC address of
the chassis in which you use the master switch as the stack MAC address.
The stack continues to use the master’s chassis MAC address even after a failover. The MAC address is not refreshed until the
stack is reloaded and a different unit becomes the stack master.
NOTE: If the removed management unit is brought up as a standalone unit or as part of a different stack, there is a
possibility of MAC address collisions. If you add a standalone unit, which has the same priority as the master stack unit, the
standalone unit joins the stack as a member unit.
Stacking LAG
When multiple links are used between stack units, Dell Networking OS automatically bundles them in a stacking LAG to provide
aggregated throughput and redundancy.
The stacking LAG is established automatically and transparently by Dell Networking OS (without user configuration) after
peering is detected and behaves as follows:
● The stacking LAG dynamically aggregates; it can lose link members or gain new links.
● Shortest path selection inside the stack: If multiple paths exist between two units in the stack, the shortest path is used.
High Availability on S5000 Stacks
An S5000 stack has a master and standby management unit that provide redundancy in a similar way to redundant route
processor modules (RPMs).
As shown in the following example, the show redundancy command displays the status and configuration of redundancy in
the stack.
The master unit synchronizes the running configuration and protocol states so that the system fails over in the event of a
hardware or software fault on the master unit. In such an event, or when the master unit is removed, the standby unit becomes
the stack manager and Dell Networking OS elects a new standby unit. Dell Networking OS resets the failed master unit: after
online, it becomes a member unit; the remaining members remain online.
Example of S5000 Stack Manager Redundancy
Stack#show redundancy
-- Stack-unit Status --
----------------------------------------
Mgmt ID: 0
Stack-unit ID: 1
Stack-unit Redundancy Role: Primary
Stack-unit State: Active
Stack-unit SW Version: 9.1(1.0)
Link to Peer: Up
-- PEER Stack-unit Status --
---------------------------------------
Stack-unit State: Standby
Peer stack-unit ID: 2
Stack-unit SW Version: 9.1(1.0)
-- 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
Stacking
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